Re: Simultaneous refinement of multiple atoms sharing same site

[Leonid Solovyov]

>how three atoms, sharing the same xyz position, could be refined in terms of 
>their occupancies via FullProf

One of many possible options is to set 11.0 for one atom and -10.5 for the two 
others.

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***






On Saturday, August 31, 2019, 9:46:50 PM GMT+7, Ahmed Subrati 
 wrote: 







Dear all,





I wanted to ask how three atoms, sharing the same xyz position, could be 
refined in terms of their occupancies via FullProf. We know that for the case 
of two atoms, the first atom is set as 11.0 and the second one as -11.0 so that 
their sum is unity, but how would be the case for three atoms.





Thank you very much.





King regards,

Ahmed Subrati


PhD student

NanoBioMedical Centre | Adam Mickiewicz University in Poznan, Poland


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[SUSPECTED SPAM] Re: Rietveld

[Leonid Solovyov]

>That is why I prefer to use Rietveld's original term "profile refinement" for 
>all kinds of powder pattern refinement, and reference Loopstra and Rietveld 
>(1969) instead of >just Rietveld (1969)

In the Introduction of Loopstra and Rietveld (1969) they referred to the 
approach as "the profile refinement technique (Rietveld, 1967, 1968)" and give 
some important expressions for the refinement procedure that were absent in 
Rietveld (1967). So, a more correct citation for the profile refinement 
technique would be (Rietveld, 1967, Loopstra & Rietveld, 1969).


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*** 

On Wednesday, August 22, 2018, 3:02:48 PM GMT+7, Alan Hewat 
 wrote:  
 
 Leonid. Rietveld's code is indeed a specific type of profile refinement. 
Structure parameters are refined to fit the observed profile intensities using 
a least squares code similar to that used to fit integrated Bragg intensities 
at Oak Ridge - ORFLS (1962). From 1961 profile refinement methods were used at 
Argonne to fit multiple peaks to profile intensities, and later at Petten. All 
references are given in  vL&S.
Unfortunately, the term "Rietveld method" has been applied to types of profile 
refinement that are closer to earlier profile refinement methods, such as 
refining the proportions of different phases where the individual structures 
are known.
That is why I prefer to use Rietveld's original term "profile refinement" for 
all kinds of powder pattern refinement, and reference Loopstra and Rietveld 
(1969) instead of just Rietveld (1969). I would also call quantitative phase 
analysis from powders "profile refinement" rather than Rietveld refinement, and 
reference Werner et al. (1979).
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
  from my tablet
 +33.476.98.41.68
        http://www.NeutronOptics.com/hewat
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Re: Rietveld

[Leonid Solovyov]

>Gauss and Legendre's work shows that science is not performed by individuals 
>in a vacuum. >Now we call it "Least Squares Refinement" and not "Gauss 
>Refinement".

It seems that the basic collision is in the absence of strict and commonly 
accepted definition of the 'Rietveld Method' term. Does the Rietveld method 
imply:
1) a general concept of structure refinement using powder data in their 
original form of scanned profile,
or

 2) just one (of many possible) specific realization of this concept as a least 
squares optimization of weighted profile difference?
I'd prefer the second variant, which may also help resolving the issue of 
credits and citations.


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*** 

On Wednesday, August 22, 2018, 11:52:03 AM GMT+7, Alan Hewat 
 wrote:  
 
 >  credit should be given to Rietveld for developing and distributing his 
 >software No-one is disputing that, even if Rietveld himself never gave credit 
 >to anyone else. In Rietveld (1969) he merely `thanks Drs B. O. Loopstra and 
 >B. van Laar for their suggestions and helpful criticism'. Yet according to 
 >vL&S he had been hired as a postdoc to contribute to a problem they had been 
 >working on.. His home page is an extreme example, where others are only 
 >credited for their hommage to him. 
Gauss and Legendre's work shows that science is not performed by individuals in 
a vacuum. Now we call it "Least Squares Refinement" and not "Gauss Refinement".
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
 +33.476.98.41.68
        http://www.NeutronOptics.com/hewat
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Re: Something to read...

[Leonid Solovyov]

Yes, the figures are impressive! I wonder what kind of Bayesian insight one 
should have to see that "in Fig. 6. The difference curve demonstrates that 
Bayesian inference method better reproduces the observed diffraction profiles" 
?? 
It seems that the open-access article charge serves as an indulgence for any 
speculation. 


 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***




From: Alan Hewat 
To: Jonathan Wright  
Cc: "rietveld_l@ill.fr" 
Sent: Friday, August 26, 2016 1:58 PM
Subject: Re: Something to read...



http://www.nature.com/articles /srep31625 on "Full Diffraction Profile Analysis"

I like figure 1 and look forward to seeing the method applied to quantify 
uncertainty by appropriately
modeling the heteroskedasticity and correlation of the error structure in 
something other than silicon.


Alan

__

   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat

__

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Re: structure solution terminology

[Leonid Solovyov]

>What's the right nickname for the method of structure solution from powders

In Russian we use an equivalent to 'structure decipher'.
Sometimes, however, this is really 'structure solution' when we apply vodka in 
the process ;)

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


On Thu, 12/17/15, Lubomir Smrcok  wrote:

 Subject: structure solution terminology
 To: rietveld_l@ill.fr
 Date: Thursday, December 17, 2015, 5:05 AM
 
 Hi,
 
 I feel I have a problem with terminology. What's the right
 nickname for 
 the method of structure solution from powders, which instead
 of analyzing 
 electron (nuclear) density shuffles atoms or molecules
 around a cell and 
 compares experimental and calculated patterns ? It could be
 well used also 
 for single crystal data, I know, but it is not routinely
 done (yet ?).
 
 I remember that colloquially used phrase "structure solution
 in direct 
 space" woke me up several times during plenary lectures at
 several 
 conferences. What are we having in direct space ? IMHO just
 electron 
 (nuclear) density. Its FT is our diffractogram so that if we
 fit 
 diffractogram, are we still in direct space ? Of course,
 reciprocal space 
 is a pure math and diffracted beam is quite realistic (BTW,
 are 
 there photons also in reciprocal space :-) ?). But in which
 space are we when doing any 
 crystallographic calculation ? OK, OK, you know what I am
 asking ... no 
 bad jokes, please.
 
 May I ask for your 2 cents ?
 Thanks,
 Lubo
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Re: Selective peak broadening - interpretation and handling in FullProf

[Leonid Solovyov]

Dear Kotaro, 

The microstructure-related peak broadening always increase with 2Theta (and 
decrease with d). 
In your case, I suspect, the increase of FWHM with d might be due to an 
instrumental contribution, as the general trend looks similar to that of the 
CeO2 standard. 

Best regards, 
Leonid 

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Kotaro SAITO 
To: Radovan Cerny ; l_solov...@yahoo.com
Cc: "Rietveld_l@ill.fr" 
Sent: Tuesday, August 4, 2015 4:54 PM
Subject: Re: Selective peak broadening - interpretation and handling in FullProf

Dear Radovan and Leonid,

Thanks for your comments.
Both papers are very interesting and seem to contain good hints for my case.

Now I am confusing when I compare peak width vs. 2th in constant wave profiles  
and peak width vs. d in TOF.
When I plot FWHM/d vs. d, FWHM/d of all-odd peaks increases with increasing d. 
(Note these FWHM are obtained with multiple peak fitting with simple Gaussian.)
In other words, peak broadening is large for small hkl peaks.
Here is the plot. (not an attachment file!) 
https://www.dropbox.com/s/uzm0fv3q8ljoq5o/Layout0.pdf?dl=0
On the other hand, for example Fig.3 in Leonid’s paper 
(http://dx.doi.org/10.1107/S00218898114X), peak broadening is larger for 
large 2th, which means large hkl peaks.
If the peak broadening in my TOF data has a similar origin as two papers which 
Radovan and Leonid showed, is it acceptable to have such different hkl 
dependence between TOF and 2th data? Or do I miss some basic points about 
diffraction?

Best regards, 

Kotaro

//////
  Kotaro SAITO
  High Energy Accelerator Research Organization
  Institute of Materials Structure Science
  1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
//////
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Re: Selective peak broadening - interpretation and handling in FullProf

[Leonid Solovyov]

Dear Kotaro, 

The broadening you describe seems to be due to a non-uniform distribution of 
site occupancies in the crystal lattice. A general model for such 
defect-related broadening is described here: 
http://dx.doi.org/10.1107/S00218898114X 
The model is included into the DDM program (but it doesn't handle TOF data, 
unfortunately). 

Hope this helps, 
Leonid 

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Kotaro SAITO 
To: Rietveld_l@ill.fr
Cc: 
Sent: Friday, July 31, 2015 2:14 PM
Subject: Selective peak broadening - interpretation and handling in FullProf

Dear Rietvelders,

There is two things I would like to ask.

1. Physical interpretation of selective peak broadening
I have a difficulty in interpreting selective peak broadening in my TOF data of 
quaternary Heusler alloy.
All peaks for all-odd hkl reflections show significant broadening (about 25% 
increase from the instrumental resolution for small d range and 100% increase 
for large d range).
Other peaks for all-even hkl stay in the instrumental resolution for whole d 
range.
If hkl reflections for one specific direction show broadening, it might be 
easier to interpret.
But this time, it is not the case. (eg. 111 reflection shows significant 
broadening but 222 does not.)
If I write the sample's chemical formula as ABCD, 4 sites in the Heusler alloy 
along [111] direction seems to be (A,B)-(C,D)-(C,D)-(A,B) with different site 
mixing ratio according to brief analysis.
One thing I have noticed is that each lattice plane for all-odd hkl consists of 
one sublattice.
For the case of 111 reflection, which is the easiest case, first plane at the 
origin consists only (A,B). Second plane consists only (C,D), and so on.
This holds for other all-odd hkl reflections
Does anyone know good literatures to get some hints for this?
I have checked “Defect and Microstructure Analysis by Diffraction” by Snyder, 
Fiala, and Bunge, but I couldn’t find descriptions about selective peak 
broadening.

2. Handling selective peak broadening in FullProf
The manual says “there is a number of size models built into FullProf 
corresponding to particular sets of reflections that are affected from 
broadening.”
But I only find Size-Model=14 and -2 (to -9) in the manual for that purpose. 
Are there any models other than these?
And, does anyone know what Size-Model=14 is?
The manual only shows a result using Size-Model=14 (Figure 2) without any 
explanations.
I have already tried Size-Model=-2 and it works well but not sufficient for 111 
peak which shows the largest broadening. (and it does not gives me any physical 
interpretation, of course.)

Best,

Kotaro


//////
  Kotaro SAITO
  High Energy Accelerator Research Organization
  Institute of Materials Structure Science
  1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
//////
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Re: Peak assymtery not able to fit

[Leonid Solovyov]

Dear Lubo,

“Funny” shape is not that indicative. More important is that the second (020) 
peak appears notably broader that the first (111) peak, which is characteristic 
of the faulting.

Best regards,
Leonid

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Lubomir Smrcok 
To: Leonid Solovyov 
Cc: rietveld_l@ill.fr
Sent: Monday, June 15, 2015 3:21 PM
Subject: Re: Peak assymtery not able to fit

Well,
I do not work with metals and therefore my question could be somehow 
naive. 
Suppose you have such funny peaks and you are sure it is not due to 
experimental conditions. How unique is than  the interpretation offered by 
Leonid ? Nothing presonal, of course :-)
lubo
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Re: Peak assymtery not able to fit

[Leonid Solovyov]

Dear Apu, 

As the 2nd peak seems to be broader than the 1st one, the broadening is most 
probably due to the stacking faults, typical for the close-packed metals. The 
asymmetry and complexity of the broadening might also suggest the presence of 
crystallites with different degree of faulting (and/or size). Among DDM ( 
http://sites.google.com/site/ddmsuite ) examples there is a model for Cu ( 
\DDM195d\EXAMPLES\Defects\Cu.ddm ), accounting for the influence of faults on 
both peak broadening and intensities. It may also be applicable to Ni, but in 
this particular case a two-phase model might be necessary to allow for the 
presence of different crystalline fractions. 

Best regards, 
Leonid 
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Apu Sarkar 
To: "rietveld_l@ill.fr"  
Sent: Monday, June 15, 2015 12:59 PM
Subject: Peak assymtery not able to fit



Hi,

I am working on a nanocrystalline Nickel sample. I am not able to fit the peaks 
to get FWHM and Integral Breadth. 

Please see the attached images. Fig. 1 shows the profile and a zoomed view of a 
peak. Tail part of the peak is broader. 

Fig. 2 shows the winplotr fit. It is not matching the max intensity.

Please give you suggestions to get a better fit for this kind of XRD peak.


Thanks
Apu

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Re: Experimental and calculated RIRs of metals from ICDD

[Leonid Solovyov]

>Experimental RIRs are trash? theoretical RIRs do not represent at all any 
>reasonable experimental >system? there is not error bar in RIR? Let us do 
>Rietveld and be very careful to properly account for >microabsorption... 


Good questions and suggestion… 
For those who are interested, I have an XRD pattern (Co radiation) of an 
artificial mixture of Cu and Zn powders: 
https://sites.google.com/site/ddmsuite/home/CuZn_powder.xy 
The microabsorption can be neglected for this mixture, but the questions: 
“Experimental RIRs are trash? theoretical RIRs do not represent at all any 
reasonable experimental system?” are highly actual. 
>From Rietveld I was unable to reproduce correct weight-fractions within 
>reasonable limits. If somebody can, I would highly appreciate. 
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Leopoldo Suescun 
To: "rietveld_l@ill.fr"  
Sent: Thursday, June 11, 2015 3:37 PM
Subject: Re: Experimental and calculated RIRs of metals from ICDD



Experimental RIRs are trash? theoretical RIRs do not represent at all any 
reasonable experimental system? there is not error bar in RIR? Let us do 
Rietveld and be very careful to properly account for microabsorption...




2015-06-11 4:18 GMT-03:00 Alan Hewat :

Hi Leonid.
>
>
>I can't answer your question, but want to warn you that Gmail put your email 
>into my spam folder with the following explanation: "Why is this message in 
>Spam? It has a from address in yahoo.com but has failed yahoo.com's required 
>tests for authentication".
>
>
>I don't understand Gmail's tests, and this problem is not due to the Rietveld 
>server. Your message was distributed and is already in the archive 
>http://www.mail-archive.com/rietveld_l@ill.fr/ but Gmail users (there are a 
>lot) may miss your message unless they manually check their spam folder.
>
>
>For all Rietveld list members - if your message to the list is rejected, it 
>will be because the email address you are using is not identical to that with 
>which you subscribed. If your address changes, you must subscribe again to be 
>able to post, even though you may still RECEIVE messages via forwarding. This 
>list is not moderated. Whether your message is posted or not is entirely 
>decided by the SYMPA server software.
>
>
>Alan.
>
>
>On 11 June 2015 at 08:07, Leonid Solovyov  wrote:
>
>Dear Rietveldians,
>>
>>Can anybody give an explanation of a severe discrepancy in the experimentally 
>>measured Reference Intensity Ratios (RIR) and those calculated from structure 
>>for some metals, such as Zn, Ti, Cd etc. in the ICDD PDF?
>>In particular for Zn, the experimental RIR from ICDD PDF 00-004-0831 is 3.8, 
>>while the calculated RIR from PDF 01-078-9363 is 8.39. For Cd the difference 
>>is more impressive: RIR=2 in PDF 00-005-0674 and 15 in PDF 01-071-3769.
>>For the experimental RIRs a reference is given: Swanson, Tatge., Natl. Bur. 
>>Stand. (U. S.), Circ. 539, I, 16, (1953), which is inaccessible for me, 
>>unfortunately.
>>
>>Any hypothesis?
>>Leonid
>>
>> ***
>>Leonid A. Solovyov
>>Institute of Chemistry and Chemical Technology
>>660036, Akademgorodok 50/24, Krasnoyarsk, Russia
>>http://sites.google.com/site/solovyovleonid
>>***
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Experimental and calculated RIRs of metals from ICDD

[Leonid Solovyov]

Dear Rietveldians, 

Can anybody give an explanation of a severe discrepancy in the experimentally 
measured Reference Intensity Ratios (RIR) and those calculated from structure 
for some metals, such as Zn, Ti, Cd etc. in the ICDD PDF? 
In particular for Zn, the experimental RIR from ICDD PDF 00-004-0831 is 3.8, 
while the calculated RIR from PDF 01-078-9363 is 8.39. For Cd the difference is 
more impressive: RIR=2 in PDF 00-005-0674 and 15 in PDF 01-071-3769. 
For the experimental RIRs a reference is given: Swanson, Tatge., Natl. Bur. 
Stand. (U. S.), Circ. 539, I, 16, (1953), which is inaccessible for me, 
unfortunately. 

Any hypothesis? 
Leonid 

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
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++

Re: Unit cell accessible volume

[Leonid Solovyov]

>I am, however, interested in finding out
>whether inserting certain molecules
>in the voids (without distorting the structure)
>is geometrically possible.

You may use FOX: http://fox.vincefn.net/
There you can insert guest molecules into the structure cell, set up their 
flexibility (or use as rigid bodies), add AntiBump distances, and optimize the 
positions and orientations of the molecules to satisfy the best AntiBump 
“energy”.
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Othman Al Bahri 
To: "rietveld_l@ill.fr"  
Sent: Wednesday, June 10, 2015 11:40 PM
Subject: Unit cell accessible volume

Dear all,
 
I am trying to calculate the void volume in a unit cell. I can estimate the 
overall void volume manually by subtracting  the occupied space volume from the 
total unit cell volume using VESTA. I am, however, interested in finding out 
whether inserting certain molecules in the voids (without distorting the 
structure) is geometrically possible. Is there a way to do this given the 
complexity of some structures/superstructures and the large number of ways a 
molecule can intercalate into a structure ?
 
Kind Regards,
Othman Al Bahri
UNSW - Sydney
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Re: 3D powder averaging...

[Leonid Solovyov]

Dear Jon, 


Considering the link you gave: 
http://www.buzzfeed.com/lukelewis/what-british-people-say-versus-what-they-mean 
I think it would be relevant to clarify your sentence: ‘Choosing to single out 
individual publications for public abuse on a mailing list is a bit of a 
shame’. 
I believe that public discussion of publications is absolutely normal in any 
media provided the discussion is open, honest and reasoned enough. So, your 
term ‘public abuse’ is probably related to emotional comments without reasons 
and arguments. 

Best regards, 
Leonid 

***Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Jonathan Wright 
To: Alan Hewat 
Cc: rietveld_l@ill.fr
Sent: Monday, May 11, 2015 1:56 AM
Subject: 3D powder averaging...

On 2015-05-10 17:36, Alan Hewat wrote:
>> Jon... nicely illustrated... by posting an interesting link...

Thanks! Obviously I think these serial methods are a fantastic 
opportunity for this community. An IUCrJ commentary by me is here:

"Serial crystallography for the masses": 
http://journals.iucr.org/m/issues/2015/01/00/hi0136/index.html

...which is all about a paper showing that unbelievably weak and noisy 
data can be merged into a 3D dataset.

An open question is: will the new community of people developing these 
3D methods ever show up on this list? In principle Rietveld methods and 
powder experts should have a lot to offer, but until now it seems to be 
mostly protein crystallographers who are getting the beamtime at the 
FEL.

Would "point-by-point" Rietveld refinement extend to scaling and fitting 
all the snapshots? The profile function comes in as where you think each 
intensity was on the rocking curve.

> Actually I think Jon was being a little snarky himself. ...

Not entirely*, if I wanted to 'wind you up' I'd have linked something 
from electron microscopy :-) This one just came out:

http://news.sciencemag.org/biology/2015/05/electron-microscopes-close-imaging-individual-atoms

Obviously powder diffraction has a rich and exciting future, especially 
when it is used as an imaging method. Google finds this one for Rietveld 
tomography:

J. Appl. Cryst. (2011). 44, -1119[ doi:10.1107/S0021889811024423 
] "Hard X-ray diffraction scanning tomography with sub-micrometre 
spatial resolution: application to an annealed [gamma]-U0.85Mo0.15 
particle" H. Palancher, R. Tucoulou, P. Bleuet, A. Bonnin, E. Welcomme 
and P. Cloetens

There are always exciting future directions. Doubtless others will 
respond with what is new and exciting with neutrons and PDF's, etc. 
(yes, that is a challenge).

Choosing to single out individual publications for public abuse on a 
mailing list is a bit of a shame. If you write a "comment on" the 
authors get a fair chance to respond (and privately tear you apart if 
you're wrong). If your comment survives then future readers of the paper 
will be informed, which does not happen when something is posted here. 
Highlighting things which _are_ worth reading is something I always 
appreciated from Armel's contributions to the list over the years.

All the best,

Jon
===

* 
http://www.buzzfeed.com/lukelewis/what-british-people-say-versus-what-they-mean
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Re: On the “crystallographic good practices”

[Leonid Solovyov]

Dear Alan, 

The authors may have their own evidences and responsibilities, but when they 
try supporting their hypothesis by crystallography, this must be done 
correctly, especially in IUCr journals. 
As for your secret belief in triclinic nature of all crystals, I’d say that 
they are not crystals at all since they have boundaries ;) 

Best wishes, 
Leonid 
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Alan Hewat 
To: Leonid Solovyov  
Cc: Lista Rietveld  
Sent: Sunday, May 10, 2015 3:32 PM
Subject: Re: On the “crystallographic good practices”



Dear Leonid. 

You have a point, but they also have other evidence for lower symmetry. 
(Personally I have for long believed, secretly, that all structures were at 
best triclinic, and that everything else was just an average :-) I know you 
like to be provocative, but let's not start a little war over this. Normally 
the referees and journals, together with the authors, are responsible for what 
they publish.

Best wishes, Alan.
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Re: On the “crystallographic good practices”

[Leonid Solovyov]

Hi Nicolae! 

Of course, I refined in R-3c using your anisotropic strain model, which gave 
perfect results for both Fe2O3 and Cr2O3 up to anisotropic thermal parameters 
of all atoms: 
https://sites.google.com/site/ddmsuite/tutorials/Fe2O3-Cr2O3.png 
All that glitters is not gold, unfortunately ;) 

Best wishes, 
Leonid 

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: "nicp...@infim.ro" 
To: Leonid Solovyov 
Cc: Lista Rietveld 
Sent: Sunday, May 10, 2015 3:20 PM
Subject: Re: On the   =?iso-8859-1?Q?=E 2 =80=9Ccrystallogr ap hic_good_practic 
es= E2=80=9D?=

Leonid, good point!
Molodetz! Pozdravliaiu!
Have you refined in R-3c?
Nicolae Popa
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On the “crystallographic good practices”

[Leonid Solovyov]

Regarding the query of Leopoldo Suescun:
”Shouldn´t the IUCr take action and try to influence the journals that
frequently publish x-ray data (as a complementary characterization
technique but that determines the validity of other results) to have
well-trained crystallographers review any article that contains x-ray
diffraction data?”

Unfortunately, the issue of crystallographic review is problematic even in the 
IUCr journals, especially for powder data. A fresh instance from Acta B:
http://dx.doi.org/10.1107/S205252061500342X
where the crystal structures of alpha-Fe2O3 and alpha-Cr2O3 are “re-refined” to 
be monoclinic. The monoclinic symmetry is “substantiated” by the observation of 
a “complex” peak broadening that, in fact, is well described by the anisotropic 
strain model available in all popular Rietveld programs.
With such structure validation, all crystal structures may be re-refined, 
potentially, to lower symmetry, as the anisotropic strain broadening is a 
common powder pattern feature.
If this practice is accepted in an IUCr journal, what can we expect from 
non-crystallographic literature?

 ***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
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Re: Determination of Microstrain using MAUD

[Leonid Solovyov]

Dear Lennart,

In the microstructure analysis you aim at, one should take into account 
different contributions to the peak broadening:
instrumental,
crystal size,
microstrain,
and stacking faults.
Using only two reflections (111 and 200) one can not allow for all these 
contributions independently and correctly. You should use as many reflections 
as possible from the whole powder pattern range up to the highest diffraction 
angles you can reach.
Regarding the model of stacking faults in MAUD, it has a shortcoming in that it 
does not allow for the influence of faults on peak intensities. See our recent 
discussion:
http://www.mail-archive.com/rietveld_l@ill.fr/msg05464.html
http://www.mail-archive.com/rietveld_l@ill.fr/msg05469.html

Best regards,
Leonid
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Lennart Leich 
To: Rietveld_l@ill.fr 
Sent: Friday, March 20, 2015 11:30 PM
Subject: Determination of Microstrain using MAUD



Hello everyone,
 
first I want to introduce myself. My name is Lennart Leich, I am 24 years old 
and I study mechanical engineering at the „Ruhr-Universität-Bochum“ in Germany. 
My area of specialisation is materials science and materials engineering. 
 
At the moment I writing my bachelor thesis with the topic: „Determination of 
the stacking fault energy of different fcc metals using X-ray’s” at the chair 
of materials engineering. As microstructure analysis using diffraction is not 
well known at our institute we start powder diffraction using bragg-brentano 
geometry on the pure elements nickel, gold and copper and later on a 
chrome-nickel steel. 
We want to determine the stacking fault energy by comparing diffractograms of 
annealed and cold-worked powders as described in [1].
I plan to do Rietveld Refinement using the Software MAUD to determine the 
microstrain.
 
Steps in MAUD:
1.load file data of diffractogram *.xy, *.cif and the file of 
instrumental broadening (MAUD tutorial – Instrumental Broadening Determination 
is already done) into MAUD
2.refine the (111) and (200) peak separated
3.free parameters for background, scale, basic phase and refine. 
finally free parameters for Line-Broadening model and the size-strain model 
(both Popa) and refine.
 
Is my approach generally correct? Is it necessary to have “good” starting 
parameters for refinement, which I have to calculate previously, to be 
physically correct?
 
As you all know and I have learned require such Refinements a lot of 
experience, which I not have. I think one occuring problem during refinement is 
to distinguish, wether a refinement is physically correct or just a “good” 
mathematical function, that describes the diffractograms shape. Therefore I 
subscribe to this mailinglist to discuss some of my problems regarding my work.
 
Thanks in advance.
 
Best Regards
Lennart Leich
 
[1] R. P. Reed and R. E. Schramm - „Relationship between stacking-fault energy 
and x-ray measurements of stacking-fault probability and microstrain“
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Re: isotropic displacement parameter

[Leonid Solovyov]

The reason may be in the absorption (as noted by Alan Hewat) for capillary 
samples or in the surface roughness effect for flat samples.

 
***Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Rachid Abkar 
To: rietveld_l@ill.fr 
Sent: Sunday, November 2, 2014 1:08 AM
Subject: isotropic displacement parameter



The Biso isotropic displacement parameter of each element in my refinement 
using fullprof is over 3 and negative ? but my refinement  looks good and Rwp 
is only 9 could anybody give me some advice Thanks sincerely


ABKAR RACHID

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Re: question on stacking faults

[Leonid Solovyov]

Dear Angel,
The broadening due to stacking faults is structure-dependent, so the 
expressions derived for HCP structures are applicable only to the specific 
faults in close-packed atomic arrays.A general model applicable to any 
structure is described in J Appl Cryst (2000) 338 and implemented in the DDM 
program http://sites.google.com/site/ddmsuiteSome examples are given in folder 
\EXAMPLES\Defects
Best regards,Leonid 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
  From: Angel Luis Ortiz Seco 
 To: rietveld_l@ill.fr 
 Sent: Thursday, October 2, 2014 4:42 PM
 Subject: question on stacking faults
   
Dear colleages,

I would like to calculate the stacking fault probability in an O3 structure (a 
layered compound of the type ABO2 (A=alkali element, B=transition metal 
element, O=oxygen) crystallizing in the trigonal R-3m space group (hexagonal 
axes)) from the broadening of the XRD peaks. I have read the procedure 
described in Warren book for HCP structures, but I am not clear whether or not 
I can directly apply the expressions described there for my case.

Could you please advice on this issue, and indicate proper references in case 
other expressions have to be used?

Thanks a lot,

Best regards 

Angel

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++

Re: Discrepancy in the atomic coordinates of two isostructural compounds

[Leonid Solovyov]

If you don’t
refine the anisotropic displacement parameters, this ”splitting” of Fe/Zn 
position
may merely compensate the luck of anisotropic displacements in the model.
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: rajesh thattarathody 
To: rietveld_l@ill.fr 
Sent: Thursday, June 19, 2014 1:07 PM
Subject: Discrepancy in the atomic coordinates of two isostructural compounds
 


Dear Rietvelders,


We are trying to refine the structure of InFeO3(ZnO) compound using GSAS. The 
compound crystallises in R-3m space group and Zn and Fe occupy the same 
position (00 0.2171). This result is obtained from single crystal studies of 
isostructural Ga analogue. When we try to refine PXRD of Fe analogue using 
these parameters, slight deviations (more than esd) in Fe and Zn positions are 
seen (Zn: 0.2190(1) and Fe: 0.2126 (2)). My queries are:
1.   Does this mean that x-rays can really distinguish between Fe and Zn 
and not Ga and Zn?
2.   Is this evidence of any structural ordering in terms of Zn and Fe? Or 
even a random placement of Zn and Fe is possible with these deviations?
3.   If crystallographically it is not possible, is it acceptable to fix 
one’s position based on the other?

thanking you in advance-- 
Rajesh T
Research Fellow

Catalysis and Inorganic chemistry division
CSIR-National Chemical Laboratory
Pune, India
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Re: Phase volume fraction

[Leonid Solovyov]

Dear Martin,

The main problems of the e.s.u. expressions used in Rietveld programs are the 
neglect of correlations between residuals and the loss of interrelations 
between particular residuals and particular parameters in terms of their mutual 
influence.
Some references on the topic:
J. Appl. Cryst. (1979). 12, 554-563
Acta Cryst. (1982). A38, 264-269
J. Appl. Cryst. (1983). 16, 159-163
J. Appl. Cryst. (1986). 19, 10-18
J. Appl. Cryst. ( 1991). 24, 1-5
J. Appl. Cryst. (1994). 27, 802-844

Best regards,
Leonid
***

Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Martin Fisch 
To: Leonid Solovyov  
Sent: Friday, May 2, 2014 2:59 PM
Subject: Re: Phase volume fraction
 


Hi Leonid

Everyone says that Rietveld s.u.'s are underestimated. Why is this?
Is there any reference to this?

Cheers,
Martin



On 02.05.2014 09:57, Leonid Solovyov wrote:

Dear Apu,
>
>
>If you use the Rietveld-based QPA you may assess the detection limit for a 
>phase from the estimated standard uncertainty of its weight (or volume) 
>fraction. In this case one should also take into account the fact that the 
>Rietveld standard uncertainties of QPA are underestimated about 2-3 times. To 
>have more realistic uncertainties you may use DDM:
>http://sites.google.com/site/ddmsuite/
>http://sourceforge.net/p/ddmsuite
>
>
>Best regards,
>Leonid
> 
>***
>Leonid A. Solovyov
>Institute of Chemistry and Chemical Technology
>660036, Akademgorodok 50/24, Krasnoyarsk, Russia
>http://sites.google.com/site/solovyovleonid
>***
>
>
>
> From: Apu Sarkar 
>To: "Leoni, Matteo"  
>Cc: "rietveld_l@ill.fr"  
>Sent: Friday, May 2, 2014 3:41 AM
>Subject: Re: Phase volume fraction
> 
>
>Yes, I meant detection limit.
>In my sample I have a second phase which dissolves at some
>temperature. I tried to identify the dissolution
  temperature using
>XRD. With increasing temperature the peak intensity  for
  the second
>phase decreased. After certain temperature the peak
  disappeared. I
>understand that is not exactly the dissolution
  temperature. There is a
>limit of XRD to detect the phase.
>
>Thanks
>Apu
>
>Department of Nuclear Engineering
>NC State University
>Raleigh, USA
>
>
>
>On 5/1/14, Leoni, Matteo  wrote:
>> I guess you are talking about detection limit only,
  not quantification
>> limit, right?
>> The answer largely depends on your material
  (scattering power, domain size),
>> tube (sampling volume) and counting time. I have seen
  cases where you can
>> clearly see something below 0.1 wt% and cases where
  already the percent was
>> off limits.
>> Matteo
>>
>>
  -
>>
>>  Matteo Leoni, PhD
>>
>>  DICAM
>>  University of Trento
>>  via Mesiano, 77
>>  38123 Trento
>>  Italy
>>
>>  Tel +39 0461 282416    Fax +39 0461 282672
>>
>>  e-mail: matteo.le...@unitn.it
>>
  
>>
>>
>> -Messaggio originale-
>> Da: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] Per conto
>> di Apu Sarkar
>> Inviato: giovedì 1 maggio 2014 22.24
>> A: rietveld_l@ill.fr
>> Oggetto: Phase volume fraction
>>
>> Hi,
>> Can any one tell me what is the minimum phase volume
  fraction that can be
>> detected by a laboratory X-ray diffractometer. In
  there any reference for
>> this.
>>
>> I am using the new Empyrean from PANalytical.
>>
>> Thanks
>> Apu
>>
>> Department of Nuclear Engineering
>> NC State University
>> Raleigh, USA
>>
>
>
>-- 
>Apu Sarkar
>Postdoctoral Research Scholar
>Department of Nuclear Engineering
>North Carolina State University 
>
>Raleigh
>USA
>Mobile: 919-561-9244
>Website: https://sites.google.com/a/ncsu.edu/apu/
>
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>
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Re: Phase volume fraction

[Leonid Solovyov]

Dear Apu,

If you use the Rietveld-based QPA you may assess the detection limit for a 
phase from the estimated standard uncertainty of its weight (or volume) 
fraction. In this case one should also take into account the fact that the 
Rietveld standard uncertainties of QPA are underestimated about 2-3 times. To 
have more realistic uncertainties you may use DDM:
http://sites.google.com/site/ddmsuite/
http://sourceforge.net/p/ddmsuite

Best regards,
Leonid
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Apu Sarkar 
To: "Leoni, Matteo"  
Cc: "rietveld_l@ill.fr"  
Sent: Friday, May 2, 2014 3:41 AM
Subject: Re: Phase volume fraction
 

Yes, I meant detection limit.
In my sample I have a second phase which dissolves at some
temperature. I tried to identify the dissolution temperature using
XRD. With increasing temperature the peak intensity  for the second
phase decreased. After certain temperature the peak disappeared. I
understand that is not exactly the dissolution temperature. There is a
limit of XRD to detect the phase.

Thanks
Apu

Department of Nuclear Engineering
NC State University
Raleigh, USA



On 5/1/14, Leoni, Matteo  wrote:
> I guess you are talking about detection limit only, not quantification
> limit, right?
> The answer largely depends on your material (scattering power, domain size),
> tube (sampling volume) and counting time. I have seen cases where you can
> clearly see something below 0.1 wt% and cases where already the percent was
> off limits.
> Matteo
>
> -
>
>   Matteo Leoni, PhD
>
>   DICAM
>   University of Trento
>   via Mesiano, 77
>   38123 Trento
>   Italy
>
>   Tel +39 0461 282416     Fax +39 0461 282672
>
>   e-mail: matteo.le...@unitn.it
> 
>
>
> -Messaggio originale-
> Da: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] Per conto
> di Apu Sarkar
> Inviato: giovedì 1 maggio 2014 22.24
> A: rietveld_l@ill.fr
> Oggetto: Phase volume fraction
>
> Hi,
> Can any one tell me what is the minimum phase volume fraction that can be
> detected by a laboratory X-ray diffractometer. In there any reference for
> this.
>
> I am using the new Empyrean from PANalytical.
>
> Thanks
> Apu
>
> Department of Nuclear Engineering
> NC State University
> Raleigh, USA
>


-- 
Apu Sarkar
Postdoctoral Research Scholar
Department of Nuclear Engineering
North Carolina State University

Raleigh
USA
Mobile: 919-561-9244
Website: https://sites.google.com/a/ncsu.edu/apu/

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Re: Stacking faults and antiphase boundary

[Leonid Solovyov]

Dear Jon and Andreas,

I did not, actually, expect such a deep online analysis of the pattern ;-)
Yes, this small feature seems to be related to isolated 2D defects.

Best regards,
Leonid 

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Andreas Leineweber 
To: rietveld_l@ill.fr
Cc: 
Sent: Monday, April 7, 2014 2:21 PM
Subject: Re: Stacking faults and antiphase boundary

Dear all,

I think Jon is right. In the case of Cu this is the position of a (100) 
reflection of a hcp polytype. I have seen this feature in a couple of 
cases, and presence of this feature is sometimes taken as a sign for a 
two-phase character of the specimen, which need not be the case (other 
reflections from the hcp-like polytype generally are then lacking). In 
the case of Copper or alpha-Cu alloys a real two-phase character of the 
material is very unlikely. Diffax and Diffax_plus are able to model this 
feature.
The mentioned ice example is reported in some more depth in  PNAS 109 
(2012) 21259

Best regards
Andreas



  On 07.04.2014 09:05, Jonathan WRIGHT wrote:
>
> On 06/04/2014 08:06, Leonid Solovyov wrote:
>> The faulting model in DDM gives nearly perfect agreement with the 
>> experiment:
>> http://sites.google.com/site/ddmsuite/home/Copper-DDM.png
>>
>
> It looks a little bit reminiscent of this pattern for ice:
>
> http://www.science24.com/paper/15441
>
> ...but the little step at about 40.5 degrees doesn't seem to be in the 
> model? Isn't that coming from some sort of defects or diffuse 
> scattering? Not that I would attempt to model something like that, but 
> a 1D "rod" in 3D reciprocal space (coming from 2D defects) gives 
> step-like profiles in a 1D powder pattern. Although you generally only 
> know that if you've also got data from a single crystal :-)
>
> Cheers,
>
> Jon
>


-- 
Dr. Andreas Leineweber
Max-Planck-Institut fuer Intelligente Systeme
(ehemals Max-Planck-Institut fuer Metallforschung)
Heisenbergstrasse 3
70569 Stuttgart
Germany
Tel. +49 711 689 3365
Fax. +49 711 689 3312
e-mail: a.leinewe...@mf.mpg.de
home page of department: http://www.is.mpg.de/de/mittemeijer



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Re: Stacking faults and antiphase boundary

[Leonid Solovyov]

Dear Luca,

I always revise my models critically when I see reasons. The discrepancy in QPA 
between DDM and Maud is not that reason since in Maud you use biased 
intensities.
I am surprised by your statement that defects ‘should not’ influence 
intensities. To be convinced that they do influence you may try applying your 
model to the XRD pattern of pure copper from DDM examples 
(DDM195e\EXAMPLES\Defects\Cu.dat)
The faulting model in DDM gives nearly perfect agreement with the experiment:
http://sites.google.com/site/ddmsuite/home/Copper-DDM.png

Using the Warren model in Maud I was unable to get adequate results due to, 
apparently, the absence of connection between defects and intensities there.

Best regards,
Leonid 
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Luca Lutterotti 
To: rietveld_l@ill.fr
Cc: 
Sent: Friday, April 4, 2014 5:29 PM
Subject: Re: Stacking faults and antiphase boundary

>>but here we are talking about densities of stacking faults around 1%
(thatis anyway quite a high value for these alloys).
>>Your quantification was less than that. Now it means you have one cell
every 100 affected for the intensities. How much change do you expect to
have? Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3
if Iremember). Then you have the B factor trying to compensating the
wrong intensities given by this too high occupation. But it alters even
more the quantification.
>
> In the DDM-input file the column N contains N of atoms per unit cell,
not the occupancy. This is written in the manual. So, the total
occupancy of the additional (0,0,1/3) position (by Zn + Cu) is around
0.13, which is high enough to notably affect the intensities. If you
don’t take this effect into account you have biased results.

In fact as I said, this is the problem, it should not, given the low
density of such defects. But I see you are not willing to revise
critically your model. So the discussion will go nowhere and will actually
a bit boring for the other, so for my part it end here. If you wish to
really check the model, I am available in "private" by email.

>
> Regarding the sample, I’m not ready to discuss its properties here as
I did not work with it.

Well, this is not my way to work. When the results are against the
physical laws I am always trying to find the reason. We can make easily
errors (more than nature).

Best regards,

Luca

>
> ***
> Leonid A. Solovyov
> Institute of Chemistry and Chemical Technology
> 660036, Akademgorodok 50/24, Krasnoyarsk, Russia
> http://sites.google.com/site/solovyovleonid
> ***
>
>  
>
> - Original Message -
> From: Luca Lutterotti 
> To: Leonid Solovyov 
> Cc: Luca Lutterotti ; "rietveld_l@ill.fr"

> Sent: Friday, April 4, 2014 1:20 PM
> Subject: Re: Stacking faults and antiphase boundary
>
> Sorry Leonid,
>
> but here we are talking about densities of stacking faults around 1%
(that is anyway quite a high value for these alloys). Your
quantification was less than that. Now it means you have one cell every
100 affected for the intensities. How much change do you expect to have?
> Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3 if I
remember). Then you have the B factor trying to compensating the wrong
intensities given by this too high occupation. But it alters even more
the quantification.
> Now, this sample come from a rapidly solidified ribbon. There you have
only a B2 homogeneous phase, but by thermal treatment we get the
equilibrium phases in agreement with the phase diagram (alpha phase
about 1/3 weight or volume). We ball milled some of them at different
time, all of them stay close to the 1/3 and the 48 hours ball milled
showed quite a bit more going closer to 1/2 (but if you anneal again you
get 1/3). The 1/2 it is already a bit stretched and meaning we are not
in equilibrium with the Cu-Zn composition for the two phases.
> But now in your analysis you get 2/3 which is practically impossible
from the material/alloy point of view. So there should be a problem
somewhere right?
> Cu and Zn have only one electron difference, so in X-ray even using full
Zn or Cu does not affect the intensities, but your 0,0,1/3 occupation it
does when you go to values over 0.1 (10%) that is not feasible in such
alloy.
>
> Best regards,
>
> Luca
>
>
>
>> Dear Luca,
>>
>>
>> Now I see the principal problem of your faulting model. You do not take
into account the influence of faults on the peak INTENSITIES, which is
defini

Re: Stacking faults and antiphase boundary

[Leonid Solovyov]

>but here we are talking about densities of stacking faults around 1%
>(thatis anyway quite a high value for these alloys).
>Your quantification was less than that. Now it means you have one
>cell every 100 affected for the intensities. How much change do you
>expect to have? Your occupancy of the 0,0,1/3 is way higher than
>that (nearly 1/3 if Iremember). Then you have the B factor trying
>to compensating the wrong intensities given by this too high occupation.
>But it alters even more the quantification.

In the DDM-input file the column N contains N of atoms per unit cell, not the 
occupancy. This is written in the manual. So, the total occupancy of the 
additional (0,0,1/3) position (by Zn + Cu) is around 0.13, which is high enough 
to notably affect the intensities. If you don’t take this effect into account 
you have biased results. 

Regarding the sample, I’m not ready to discuss its properties here as I did not 
work with it.

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***

 

- Original Message -
From: Luca Lutterotti 
To: Leonid Solovyov 
Cc: Luca Lutterotti ; "rietveld_l@ill.fr" 

Sent: Friday, April 4, 2014 1:20 PM
Subject: Re: Stacking faults and antiphase boundary

Sorry Leonid,

but here we are talking about densities of stacking faults around 1% (that
is anyway quite a high value for these alloys). Your quantification was
less than that. Now it means you have one cell every 100 affected for the
intensities. How much change do you expect to have?
Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3 if I
remember). Then you have the B factor trying to compensating the wrong
intensities given by this too high occupation. But it alters even more the
quantification.
Now, this sample come from a rapidly solidified ribbon. There you have
only a B2 homogeneous phase, but by thermal treatment we get the
equilibrium phases in agreement with the phase diagram (alpha phase about
1/3 weight or volume). We ball milled some of them at different time, all
of them stay close to the 1/3 and the 48 hours ball milled showed quite a
bit more going closer to 1/2 (but if you anneal again you get 1/3). The
1/2 it is already a bit stretched and meaning we are not in equilibrium
with the Cu-Zn composition for the two phases.
But now in your analysis you get 2/3 which is practically impossible from
the material/alloy point of view. So there should be a problem somewhere
right?
Cu and Zn have only one electron difference, so in X-ray even using full
Zn or Cu does not affect the intensities, but your 0,0,1/3 occupation it
does when you go to values over 0.1 (10%) that is not feasible in such
alloy.

Best regards,

Luca



> Dear Luca,
>
>
> Now I see the principal problem of your faulting model. You do not take
> into account the influence of faults on the peak INTENSITIES, which is
> definitely wrong. This explains the discrepancies in the QPA results and
> Biso.
> In the faulted crystal some layers of atoms are displaced from the ideal
> sites of the cubic close-packed lattice. These displacements give rise to
> both the peak broadening and the intensity alterations. In my model I take
> it into account by the inclusion of the additional atomic pseudo-position.
> In your model you use an idealized cubic FCC structure and, thus,
> idealized intensities which differ from the real ones due to the faulting.
> So, my quantification should not go closer to yours.
>
>  
> Best regards,
>
> Leonid
>
> ***
> Leonid A. Solovyov
> Institute of Chemistry and Chemical Technology
> 660036, Akademgorodok 50/24, Krasnoyarsk, Russia
> http://sites.google.com/site/solovyovleonid
> *******
>
>
> - Original Message -
> From: Luca Lutterotti 
> To: Leonid Solovyov 
> Cc:
> Sent: Thursday, April 3, 2014 6:33 PM
> Subject: Re: Stacking faults and antiphase boundary
>
> Dear Leonid,
>
> if you wish to know, using the trigonal space group and populating the
> 0,0,1/3 site (even keeping the same number of atoms in the cell) it
> affects the intensities. Try yourself by simulation with low broadening to
> see it better. This is what make your quantification wrong. You can try as
> a counterexample to fit the bbm48bis using the FCC model. Do not care if
> the two first peaks are displaced, focus on the intensities. You
> quantification will go closer to mine.
>
> Best regards,
>
>     Luca
>
>
> On Apr 3, 2014, at 7:16, Leonid Solovyov  wrote:
>
>> Dear Luca,
>>
>> I'm glad to see yo

Re: Stacking faults and antiphase boundary

[Leonid Solovyov]

Dear Luca,


Now I see the principal problem of your faulting model. You do not take into 
account the influence of faults on the peak INTENSITIES, which is definitely 
wrong. This explains the discrepancies in the QPA results and Biso.
In the faulted crystal some layers of atoms are displaced from the ideal sites 
of the cubic close-packed lattice. These displacements give rise to both the 
peak broadening and the intensity alterations. In my model I take it into 
account by the inclusion of the additional atomic pseudo-position. In your 
model you use an idealized cubic FCC structure and, thus, idealized intensities 
which differ from the real ones due to the faulting. 
So, my quantification should not go closer to yours. 

 
Best regards,

Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: Luca Lutterotti 
To: Leonid Solovyov 
Cc: 
Sent: Thursday, April 3, 2014 6:33 PM
Subject: Re: Stacking faults and antiphase boundary

Dear Leonid,

if you wish to know, using the trigonal space group and populating the 0,0,1/3 
site (even keeping the same number of atoms in the cell) it affects the 
intensities. Try yourself by simulation with low broadening to see it better. 
This is what make your quantification wrong. You can try as a counterexample to 
fit the bbm48bis using the FCC model. Do not care if the two first peaks are 
displaced, focus on the intensities. You quantification will go closer to mine.

Best regards,

    Luca


On Apr 3, 2014, at 7:16, Leonid Solovyov  wrote:

> Dear Luca,
> 
> I'm glad to see your interest to the problem even after such a delay.
> 
>> So in the end, your model for faulting as you describe: 
>> "A more general model [J Appl Cryst (2000) 338] is included in DDM:" was to 
>> use a trigonal
>> cell with hexagonal axis to allow refining the anisotropic shift of the
>> peaks caused by the planar defects? That is a nice trick, you can try to
>> justify it by reasoning that one effect of the planar defect is to get
>> same stacking sequence of the hexagonal (we all know that), but what about
>> the FCC stacking now?
> 
> I chose the trigonal setting since the presence of layered faults decreases 
> the symmetry of the 
> material making it intermediate between cubic close-packed and hexagonal 
> close-packed. This is 
> an approximation of the real complex structure, of course, but I find it 
> applicable to most cases 
> of close-packed faulted materials I've dealt with. In some cases one has to 
> choose more 
> sophisticated models in order to account for peculiar diffraction features 
> due to correlations 
> between faults, see, for instance Fig. 2 in [O. Ersen, J. Parmentier, L. A. 
> Solovyov, M. Drillon, 
> C. Pham-Huu, J. Werckmann, P. Schultz, Direct Observation of Stacking Faults 
> and Pore 
> Connections in Ordered Cage-Type Mesoporous Silica FDU-12 by Electron 
> Tomography. 
> J. Am. Chem. Soc. (2008) 16800]
> 
>> To make the audience aware, just changing the cell was not sufficient, you
>> have to reproduce the intensities. So in the structure a couple of Cu, Zn
>> was set in 0,0,0 and another in 0,0,1/3 and the occupancies refined (to
>> values as 1.10392 for the first position and 0.39608 for the second, but
>> look like the second is calculated from the first) to adjust the
>> intensities and the density.
> 
> Yes, the additional (0,0,1/3) position is included in the model to account 
> for the partial 
> displacement of atoms from ideal CCP sites due to the faulting. It allows 
> accounting for the 
> influence of faults on both the intensities and the peak broadening according 
> to the methodology 
> described in J Appl Cryst (2000) 338.
> 
>> But actually this didn't work out completely
>> as the resulting quantitative phase analysis is completely wrong.
> 
> Why do you think that the QPA is wrong? Just because it differs from what you 
> have from 
> Maud??? 
> 
>> And where are the crystallite sizes? Planar defect densities? So what kind
>> of results did you get from the material science point of view?
> 
> I can't determine the crystallite size from this pattern since I don't have 
> the instrumental 
> broadening information. As for the faulting probability, it can be derived 
> form eq. 5 of J Appl 
> Cryst (2000) 338. For the alpha-brass phase, the fraction C of defective 
> cells (atoms displaced by 
> faults) is given by the total occupancy of the pseudo-position at (0,0,1/3) 
> that is refined to 0.132. 
>

Re: Stacking faults and antiphase boundary

[Leonid Solovyov]

u
have to reproduce the intensities. So in the structure a couple of Cu, Zn
was set in 0,0,0 and another in 0,0,1/3 and the occupancies refined (to
values as 1.10392 for the first position and 0.39608 for the second, but
look like the second is calculated from the first) to adjust the
intensities and the density. But actually this didn't work out completely
as the resulting quantitative phase analysis is completely wrong. Not to
mention a quite high B factor (2.17 compared to the near 0.6 value of Maud
and the other BCC phase) for the atoms in the alpha phase, probably to
compensate for the wrong structure and kill the two high peaks at high
angle resulting from the trigonal structure.

Well this kind of trick may be able in certain cases to fit the pattern
(here just because peaks are broad and you don't notice the split on the
first peak and others of the alpha), but the results you get speak for
themselves.
And where are the crystallite sizes? Planar defect densities? So what kind
of results did you get from the material science point of view?
You could have used just a full profile pattern fitting at this point, and
at least get the crystallite sizes. So now I am asking myself why I don't
use always a triclinic cell to describe my phases, I will have the
flexibility to fit everything without resorting to complex "physical"
models.

Best regards,

    Luca

On Jun 28, 2013, at 6:34, Leonid Solovyov  wrote:

Dear Luca,

My doubts regarding the applicability of the faulting model in Moud are
due to the absence of its description in the program and the
non-availability of options required for crystal systems where the faulted
atomic displacements and domain planes are not obviously pre-defined as in
the close-packed metals.
The model included in DDM is, indeed, simplified and phenomenological to
some extent (as well any other model) but it is equally applicable to any
structure with any crystallographic symmetry and any faulting type that
may be described by a lattice of unit cell domains differing in the atomic
arrangement. For your bbm48bis example it gives a similar profile fit as
that in Maud in both Rietveld and DDM mode with even fewer number of
variable parameters - 14 for DDM and 17 for Rietveld compared to 22 in
Maud:
http://sites.google.com/site/ddmsuite/tutorials/bbm48bis.zip
The profile R-factor output by DDM in the Rietveld mode is high (20.77%)
since it is calculated for the background-subtracted data. The equivalent
“standard” Rwp is 7.88% (and 7.59% in Maud). Some microstructural variable
parameters in the Maud model bbm48bis.par are, apparently, excessive as
their estimated errors exceed the refined values.
Concerning the FeAl.ddm example, it does contain antiphase domains whose
influence on the selective broadening is allowed for by the connection
between the pseudo-position occupancy and the size-ellipsoid (regulated by
the NDPAR field).

Best regards,
Leonid
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
From: Luca Lutterotti 
To: "rietveld_l@ill.fr" 
Sent: Wednesday, June 26, 2013 5:19 PM
Subject: Re: Stacking faults and antiphase boundary

I made a quick analysis on Leonid FeAl example.
Very simple, no stacking/twin faults, no antiphase domains, only
stoichiometry is 15% in favor of Fe. So you only fit the relative
occupancy of Al and the different sites accordingly.
So if you want to compare the two programs on that simple example, you can
download:
http://www.ing.unitn.it/~maud/FeAl.zip

there are the same files of the example of Leonid, plus I added:
FeAl_m.dat      (reformatted data file to comply with Maud dat format)
FeAl_Maud.par      (the analysis file you can load with Maud to see how
the fitting was done and what parameter I refined and occupancies
setting/binding/refinement)
FeAl_Maud_fit.pdf      (figure with the final fitting, plotted in sqrt
root of the intensities).

The step I used:
- loaded the datafile
- imported FeAl structure from Maud database
- automatic quantitative analysis
- you recognize the first peak wrong intensity, so set the binding of the
occupancies and refined both Al1, Fe1 occupancies.
- you can get lower occupancy for Al1, so fixed the Fe1 to 1 and only
refined the Al1 occupancy
- refined also the instrument asymmetry as I started with the default
instrument resolution in Maud (that has a higher asymmetry)

Now I wait for the Leonid refinement of bbm48bis (beta-brass milled 48
hours sample bis) example of Maud.

Best regards,

  Luca

On Jun 26, 2013, at 11:43 AM, Luca Lutterotti
 wrote:

Well at this point I need to post a clarification,

what Leonid call a classical treatment (Warren) is still the best and more
comprehensive theory on antiphase domain and stacking/twin faults in close
packed alloys. I to

Re: Reference Intensity Ratio of clay minerals

[Leonid Solovyov]

I'm not familiar with Jade, and from your description I may only speculate that 
such difference in calculated RIRs for the same structure may be caused by 
erroneous interpretation of the structure input files by the program (space 
group, site occupancies, etc.) or typos in the input.

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: "Chrysochoou, Maria" 
To: Leonid Solovyov 
Cc: 
Sent: Wednesday, April 2, 2014 5:07 PM
Subject: RE: Reference Intensity Ratio of clay minerals

I am using Jade to do Whole PAttern Fitting, which utilizes structural models 
like you said. Even though you cannot change the RIR because it is calculated 
from the structure, you can see it, and my understanding is that it is related 
(directly or indirectly) to the estimation of the quantities of each mineral. I 
have two different structures for vermiculite, one of which results in 1.6% VM 
(and the calculated RIR is 22) and another one which results in 6% VM (and the 
calculated RIR is 8). The fit is similar in both cases. Does this make sense?


From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Leonid 
Solovyov [l_solov...@yahoo.com]
Sent: Wednesday, April 02, 2014 5:47 AM
To: rietveld_l@ill.fr
Subject: Re: Reference Intensity Ratio of clay minerals

The Rietveld-QPA doesn’t require RIR, as the peak intensities of phases are 
calculated from the structure models. What do you mean under “doing Rietveld” 
and ”structural files” in your case?


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: "Chrysochoou, Maria" 
To: "rietveld_l@ill.fr" 
Cc:
Sent: Wednesday, April 2, 2014 4:21 PM
Subject: Reference Intensity Ratio of clay minerals

Hello,

I am wondering why the RIR of clay minerals such as vermiculite and 
montmorillonite is so high in the structural files (e.g. around 22-28). I am 
not a crystallographer, but I have noticed that high RIRs are usually 
associated with dense structures and heavy elements and neither is the case 
with clays. And for example, kaolinite and illite have much lower RIRs, 1 and 
0.5, even though the structures are not that much different. This results in 
very very low concentrations when doing Rietveld, even though there is 
substantial intensity associated with vermiculite and it does not make 
intuitive sense to me.

I would appreciate any insight into this question.

Thank you,
Maria Chrysochoou
Associate Professor
Department of Civil and Environmental Engineering
University of Connecticut
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Re: Reference Intensity Ratio of clay minerals

[Leonid Solovyov]

The Rietveld-QPA doesn’t require RIR, as the peak intensities of phases are 
calculated from the structure models. What do you mean under “doing Rietveld” 
and ”structural files” in your case?

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***


- Original Message -
From: "Chrysochoou, Maria" 
To: "rietveld_l@ill.fr" 
Cc: 
Sent: Wednesday, April 2, 2014 4:21 PM
Subject: Reference Intensity Ratio of clay minerals

Hello,

I am wondering why the RIR of clay minerals such as vermiculite and 
montmorillonite is so high in the structural files (e.g. around 22-28). I am 
not a crystallographer, but I have noticed that high RIRs are usually 
associated with dense structures and heavy elements and neither is the case 
with clays. And for example, kaolinite and illite have much lower RIRs, 1 and 
0.5, even though the structures are not that much different. This results in 
very very low concentrations when doing Rietveld, even though there is 
substantial intensity associated with vermiculite and it does not make 
intuitive sense to me.

I would appreciate any insight into this question.

Thank you,
Maria Chrysochoou
Associate Professor
Department of Civil and Environmental Engineering
University of Connecticut
++
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++

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Re: Hot stage data inconsistencies

[Leonid Solovyov]

>Our current dilemma is that our data collected at 400C and below deviates from 
>a smooth linear trend, >and this is not expected.

In oxide perovskites the oxygen vacancies may be stabilized below the 
temperature threshold at 400-500C. It can be detected by DSC measurements.


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: "Hudish, Grant" 
To: "Rietveld_l@ill.fr"  
Sent: Wednesday, April 2, 2014 3:39 AM
Subject: Hot stage data inconsistencies 




Greetings Rietvelders,

We are currently running experiments on BCZY proton conductors.  The nature of 
the runs require us to heat our samples to 1200C, then ramp down to 800C and 
collect an Xray pattern every 25C between 800 and 400C.  We then cool in 100C 
increments and collect patterns at 300, 200, 100 & RT.

We’ve been analyzing the data in TOPAS using a whole powder pattern fitting 
procedure to obtain a cubic lattice parameter at each temperature.

Our current dilemma is that our data collected at 400C and below deviates from 
a smooth linear trend, and this is not expected.  During the fitting process 
we’re letting the lattice parameter, crystallite size, strain, and sample 
height refine.  All of these values stay consistent between temperatures except 
the sample height.  For the troubled values, we see the sample displacement 
decrease as well.

Currently, we’re not sure if this is a thermal equilibrium issue with the 
sample (unlikely) or the stage (possible?), a quark of the refinement, 
something related to our ramp rate/hold time, or loosening of the stage due to 
the extended time at temperature.  We consistently have to re-tension our Pt 
strip after each 34+hr run.

Experimental details:
Anton Paar HTK 2000N hot stage
Pt heat strip
10C/min ramp rate
10min hold at temp before scan

If anyone out there has any thoughts or criticisms on the nature of our issue 
and/or refinement method they’d be greatly appreciated!

Also, does anyone have a preferred resource/reference for hot stage XRD 
methodologies?



Grant Hudish
Materials & Ceramic Engineer
CoorsTek – Research & Development
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Re: PO corrections in trigonal space groups?

[Leonid Solovyov]

Dear Mathew,

The 104 plane in calcite corresponds to the most intense reflection that is 
related, in turn, to the best "spacing" or "separation" between atomic "layers" 
along which the cleavage may occur. This is not a strict rule, of course, as 
real cleavage planes may be different depending on specific interatomic 
interactions in the crystal and other aspects, but it works in many cases.
Note also, that the 104 plane in the hexagonal setting has several 
symmetry-equivalents, while most Rietveld programs normally generate only one 
equivalent hkl for each diffraction peak, which makes the uniaxial 
March-Dollase PO correction invalid for such peculiar directions. This problem 
is resolved in DDM, where I included a special expanded-hkl option to generate 
all equivalent hkl's for every peak. About other programs I'm not sure.

Best regards,
Leonid
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



From: Matthew Rowles 
To: "Sitepu, Husinsyah"  
Cc: "daniel.chateig...@ensicaen.fr" ; 
"rietveld_l@ill.fr"  
Sent: Wednesday, March 26, 2014 8:16 AM
Subject: Re: PO corrections in trigonal space groups?



Thanks for your replies.

Husin, is there any justification for the use of the 104 direction in calcite, 
other than this is the direction that works? I'm all for doing it if it works, 
but I'd like a little theoretical backup.

Thanks Daniel. I'll put something together for a look-see. What corrections are 
being used in Maud? Are there any papers on them?

THanks

Matthew
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"a 32 years story involving Pawley and Le Bail methods + DFT"

[Leonid Solovyov]

Dear
Colleagues,
 
Since the
SDPD group apparently disappeared from Yahoo, I’m answering a query raised there
some time ago using this yet unrestrained list. The query record is attached
after the message.
 The crystal
structure solution of decafluorocyclohexene announced in the SDPD list as “a 32
years story involving Pawley and Le Bail methods + DFT” is found to be
incomplete. Now the structure is completed by an additional alternative
molecular orientation and successfully refined using original neutron powder 
data:
http://dx.doi.org/10.1107/S2052520613031028
 
So, DFT is
a powerful and useful tool, indeed, but real reliable structure solution still
requires careful analysis of experimental data.
 
DFT is DFT,
but it doesn’t guarantee. ;-)
 
Best
regards,
Leonid
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
“a 32 years story involving Pawley and Le Bail methods + DFT” history:


Hi,
 
C6F10 was
chosen long ago as the test case for demonstrating the
abilities
of a new method suggested by Pawley (1981) for accurate
extraction
of peak positions and intensities from powder diffraction
scans.
http://dx.doi.org/10.1107/S0021889881009618
 
Funny
enough, the structure awaited 2013 to be determined by a
combination
of Le Bail method, direct space structure solution and
DFT, using
the Pawley original neutron data :
http://dx.doi.org/10.1107/S2052519213013365
 
No doubt
that improvement is still possible.
 
Best
wishes,
 
Armel
 
 
>Funny
enough, the structure awaited 2013 to be determined by a
>combination
of Le Bail method, direct space structure solution and
>DFT,
using the Pawley original neutron data:
>http://dx.doi.org/10.1107/S2052519213013365
 
Rather
eccentric choice of data in the form of a simulated pattern. It seems that in
the future structures will be solved without experiment.
A
comparison of the real powder pattern with a calculated one based on the solved
structure model gives a horrible fit:
http://sites.google.com/site/ddmsuite/home/C6F10-LeBail-DFT.png
 
Something
is apparently wrong in the proposed structure model (or in the data).
 
***
Leonid A.
Solovyov
Instituteof Chemistryand Chemical Technology
660049, K.
Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
 
 
>Something
is apparently wrong in the proposed 
>structure
model (or in the data).
 
Yes. Some
ice maybe ? I don't know. It was not sure that the 2-theta max was
really ~54°
(wavelength ~1.9 A, neutron, D1A), a 
long search
for the original data
failed, so
that the Pawley extracted intensities were used.
 
But I
wanted to give you another chance to apply 
your vision
of structures refined
without
restraints. In that case, 64 x,y,z 
coordinates
and ~90 largely overlapping
peaks. Is
that your limit ? No model improvement that time ? I must say that it
was even my
limit for refinement with soft 
restraints
;-), hence the DFT approach,
but the
solution stage could even be realized routinely by DASH (etc).
 
Possibly
someone there in the world is currently making again the experiment
in order to
obtain better data... Wait & see. We already waited 32 years...
 
Best,
Armel
 
>long
search for the original data
>failed,
so that the Pawley extracted intensities were used.
 
The
original pattern is readily available in the data-file of the Pawley's program
ALLHKL:
http://www.ccp14.ac.uk/solution/pawley/allhkl/inifile.txt
 
>But I
wanted to give you another chance to apply 
>your
vision of structures refined
 
Before the
refinement one needs to find a valid structure model. So, in the future,
probably...
 
***
Leonid A.
Solovyov
Instituteof Chemistryand Chemical Technology
660049, K.
Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
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Re: on high pressure data indexing and unit cell reduction

[Leonid Solovyov]

Unit cell
standardization may be done in VESTA
http://jp-minerals.org/vesta
Load a CIF
to VESTA and go to Utilities->Standardization of Crystal Data
then File->Export
Data
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Tuesday, March 4, 2014 3:56 AM, "Young, Lindsay" 
 wrote:
 
 
 
Hello all - I've gotten stuck at a point in my data refinement, I'd appreciate 
it if someone has any suggestions for me.


I have been trying to index high pressure data. It was collected using a 
diamond anvil cell with a 2d detector. I integrated the data on GSAS II, using 
the penetration correction. I opened this data on Jade to do peak fitting, and 
indexed the resulting peak list in Topas. I managed to get a reasonable 
monoclinic cell - but it is not in standard cell notation - the angle for beta 
is 142 degrees, and I would like see this cell represented such that is between 
90 and 130 degrees. 


I tried indexing this peak list in Treor and Dicvol, with no results. I then 
tried putting the unit cell from Topas into hklgen, taking the peaks it 
generated (which do match those in the pattern), and indexing them with Treor 
and Dicvol, but neither program turns out any results. I did tweak the standard 
settings of both programs to try to get results, but this was not successful. 


The idea is, if we can get the same result in another program as we did in 
Topas, it could further show that the result is correct. 


Does anyone know how I can convert this cell? Is there a unit cell reduction 
program I could use? If you need any additional information please let me know!

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Re: quantitative analysis - perovskites - preferred orientation

[Leonid Solovyov]

Dear Lukasz,

First of all, in the majority of Rietveld programs the uniaxial preferred 
orientation (such as [100]) can not be handled adequately for cubic systems 
since the programs normally generate only one symmetrically equivalent hkl for 
a diffraction peak. In DDM, for such cases, I included a special option 
(Expanded hkl) to generate all equivalent hkl's for every peak. This option 
makes the refinement process slower and also may require some manual settings 
for initial parameter values.
Another alternative for cubic systems is spherical harmonics.
As for the estimated error of the refined PO component, it's really wise to 
check if it exceeds the refined value, but it should be done at the final stage 
only, as at initial stages all errors may be high due to the incompleteness of 
refinement.

Best regards,
Leonid
***

Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Thursday, February 6, 2014 5:37 PM, Łukasz Kruszewski 
 wrote:
 
Dear Madam/Sir(s),

I am performing Rietveld analysis for a sample containing perovskites
(CaTiO3 and SrTiO3). When putting-in a preferred orientation (PO)
correction (100 direction, as the crystals are cubic-like), I obtain
better Rwp and GOF i.e. chi-squared values (9.63 and 1.5, respectively)
than in the case of not using this correction (Rwp = 10.62 and GOF =
1.65). However, the values of the PO corrections are higher than the
errors calculated. All the other parameters including the graphical fit,
background etc., seem to be unchanged. I am also convinced about the
correctness of any input, with my diffractometer calibrated with LaB6 and
Si standards, and Beq / Uiso parameters taken directly from the CIF files
provided, so that the microabsorption factor may likely be rejected (?).
My guess is that putting in the preferred orientation might artificially,
somehow, make the fit better, maybe due to some interdependence?

Could you please kindly suggests if obtaining better statistics (Rwp, GOF)
by getting a correction values below the corresponding errors could be
treated as a good result?

Best regards!

-- 
Łukasz Kruszewski, Ph.D., adjunct
Polish Academy of Sciences
Institute of Geological Sciences
X-Ray Diffraction Laboratory (coordinator)
Twarda 51/55 str.
00-818 Warsaw
Poland
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Re: X-ray diffraction laboratory manager position

[Leonid Solovyov]

>PhDs find more convenient to use a phone rather than a screwdriver


Phone
instead of screwdriver???
It must be a SMARTphone I guess…

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Saturday, December 7, 2013 2:02 PM, Armel Le Bail  wrote:
 
Hi,

Well, after >30 years in a X-ray lab, I conclude that both technicians and 
PhDs find more convenient to use a phone rather than a screwdriver for 
calling the manufacturer in case of serious dysfunctionment...

Best,
Armel 



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++

Re: X-ray diffraction laboratory manager position [faked-from]

[Leonid Solovyov]

>Why are there so few job opportunities for people who have a Masters degree?
 
‘Cause it’s
well known that PhDs do much better than non-PhDs ;-)
Imposing PhD-requirements
for such positions is risky, in fact, as a real successful PhD won’t be 
interested
and they will get a politician instead.

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Friday, December 6, 2013 9:14 PM, "Mibeck, Blaise"  
wrote:
 

Why are there so few job opportunities for people who have a Masters degree?

I believe this job would be ideal for a MS who has 5 or so years of lab 
experience.  





From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Simon 
Redfern [s...@cam.ac.uk]
Sent: Friday, December 06, 2013 4:23 AM
To: rietveld_l@ill.fr
Subject: Re: X-ray diffraction laboratory manager position [faked-from]

Exactly so, Jon. This is the sort of job that a good candidate can make much 
of. I don't think it is described as a technician anywhere in the 
advertisement, but in any case, technical support jobs may require a high 
degree of training and education, so that in itself is not a discriminator. 
There are technicians and technicians, just as there are engineers and 
engineers.

Our X-ray lab manager has a PhD, is a skilled crystallographer, and deals with: 
instrument maintenance and support, new instrument planning, data analysis, 
interpretation, and scientific support to users who may not be expert. The role 
covers tuition to graduate students and outside users. It extends to 
scheduling, financial management, and reporting, and to contributions and 
authorship on some of the scientific papers that come out of the work of the 
lab. In many ways the role has similarities to a beam line scientist at a large 
scale facility, but with more reasonable working shift patterns (our X-ray lab 
manager actually also helps out in synchrotron and neutron campaigns).  Could 
beam line scientists be described as lab technicians? Not if you hope to return 
and get help with your next synchrotron/neutron experiment!

My observation is that for a proactive individual, this sort of position may 
offer significant scientific opportunities that extend well beyond wielding a 
screwdriver.

Simon Redfern

Professor of Mineral Physics
Department of Earth Sciences
University of Cambridge
Downing Street
Cambridge  CB2 3EQ  UK

w +44122475
m +447530312963
f +44122450


On 6 Dec 2013, at 08:32, Jonathan WRIGHT wrote:

> Did I click on the right link? The second point says:
>
> "Develop new experimental approaches and measurement routines as
> required by a growing user base."
>
> It doesn't sound so bad, unless the candidate can't think of any novel 
> experimental techniques to invent.
>
> Jon
>
>
> On 05/12/2013 19:02, Cline, James Dr. wrote:
>> Here is a position that looks a lot like what could be described as a
>> lab technician (no science anyway) and yet they require a PhD???
>>
>> How could anyone recommend a specialization in the powder diffraction
>> technique if this is all that is available?
>>
>> I find this very disconcerting.
>>
>> Jim
>>
>>
>> James P. Cline Materials Measurement Science Division National
>> Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113
>> / Bldg 217 ] Gaithersburg, MD 20899-8523    USA jcl...@nist.gov (301)
>> 975 5793 FAX (301) 975 5334
>>
>> -Original Message- From: rietveld_l-requ...@ill.fr
>> [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Suchomel, Matthew R.
>> Sent: Tuesday, December 03, 2013 7:56 PM To: rietveld_l@ill.fr
>> Subject: Fwd: X-ray diffraction laboratory manager position
>>
>> Dear Colleagues
>>
>> On behalf of Prof. Jacob Jones, I am passing along the link below for
>> an open position of X-ray diffraction laboratory manager position at
>> North Carolina State University which may be of interest to someone
>> in our community.
>>
>> . X-ray diffraction laboratory manager:
>> https://jobs.ncsu.edu/postings/30892
>>
>>
>>
>> On Nov 27, 2013, at 14:46 , Jacob Jones  wrote:
>>
>> The Analytical Instrumentation Facility (AIF) at North Carolina State
>> University  is now seeking to fill multiple staff and postdoctoral
>> positions in the areas of electron microscopy and X-ray diffraction.
>> Positions are detailed in the links provided below. We are looking to
>> hire as soon as possible, but our first priority is finding the best
>> candidates to fill these positions. Please forward this information
>> to those who may have an interest in applying.
>>
>> . X-ray diffraction laboratory manager:
>> https://jobs.ncsu.edu/postings/30892
>>
>> Regards,
>>
>> Jacob L. Jones Associate Professor, Department of Materials Science
>> and Engineering Director, Analytical Instrumentation Facili

Re: X-ray diffraction laboratory manager position

[Leonid Solovyov]

If scientists aren't supposed to know how to use screwdrivers, then the 
position definitely requires PhD ;-)

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Friday, December 6, 2013 5:59 PM, Alan Hewat  
wrote:
 
Could beam line scientists be described as lab technicians? Not if you hope to 
return and get help with your next synchrotron/neutron experiment!
I hope that's not the only reason :-) Good to see some end-of-year banter on 
the Rietveld list. As Leonid shows, in Europe titles are important. But in the 
US asking for a Ph.D. simply indicates the level of experience required. 
Otherwise a person is judged on his performance not his title. 

Talking of screwdrivers, when I worked in the UK (some time ago) scientists 
weren't supposed to know how to use them. Technicians performed experiments and 
scientists analysed and published the results. This attitude still colours 
relations at large scale user facilities. 


Alan
__
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
 +33.476.98.41.68
        http://www.NeutronOptics.com/hewat

__ 

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Re: X-ray diffraction laboratory manager position

[Leonid Solovyov]

If PhD is
required even for politicians, why technicians should be the minorities?
 
http://www.dw.de/tempting-phds-lead-politicians-into-plagiarism/a-16595782
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Friday, December 6, 2013 1:05 AM, "Cline, James Dr."  
wrote:
 
Here is a position that looks a lot like what could be described as a lab 
technician (no science anyway) and yet they require a PhD???  

How could anyone recommend a specialization in the powder diffraction technique 
if this is all that is available?  

I find this very disconcerting.  

Jim


James P. Cline
Materials Measurement Science Division  
National Institute of Standards and Technology
100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ]
Gaithersburg, MD 20899-8523    USA
jcl...@nist.gov
(301) 975 5793
FAX (301) 975 5334


-Original Message-
From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of 
Suchomel, Matthew R.
Sent: Tuesday, December 03, 2013 7:56 PM
To: rietveld_l@ill.fr
Subject: Fwd: X-ray diffraction laboratory manager position 

Dear Colleagues 

On behalf of Prof. Jacob Jones, I am passing along the link below for an open 
position of X-ray diffraction laboratory manager position at North Carolina 
State University which may be of interest to someone in our community.

. X-ray diffraction laboratory manager:
https://jobs.ncsu.edu/postings/30892



On Nov 27, 2013, at 14:46 , Jacob Jones  wrote:

The Analytical Instrumentation Facility (AIF) at North Carolina State 
University  is now seeking to fill multiple staff and postdoctoral positions in 
the areas of electron microscopy and X-ray diffraction. Positions are detailed 
in the links provided below. We are looking to hire as soon as possible, but 
our first priority is finding the best candidates to fill these positions. 
Please forward this information to those who may have an interest in applying. 

    . X-ray diffraction laboratory manager: https://jobs.ncsu.edu/postings/30892

Regards,

Jacob L. Jones
Associate Professor, Department of Materials Science and Engineering Director, 
Analytical Instrumentation Facility North Carolina State University Raleigh, NC
Email: jacobjo...@ncsu.edu
Phone: 919-515-4557


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Re: phase id for Friday refreshment

[Leonid Solovyov]

Dear Mikko,

Your XRD pattern is well approximated by an orthorhombic Pbcn structure with 
lattice parameters a=5.187,   b=5.607,   c=5.311, which may present a new 
anisotropically disported polymorph of cubic (Ce?,Sn?)O4.

Best regards,
Leonid
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On , Leonid Solovyov  wrote:
 
Dear Mikko,

Your XRD pattern is well approximated by an orthorhombic Pbcn structure with 
lattice parameters a=5.187,   b=5.607,   c=5.311, which may present a new 
anisotropically disported polymorph of cubic (Ce?,Sn?)O4.

Best regards,
Leonid
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Friday, October 25, 2013 2:33 PM, Mikko Heikkilä 
 wrote:
 
Dear Rietvelders,
 
I decided to completely embarrass myself and ask you a simple phase 
identification question. I’ve had some trouble in trying to figure out what’s 
going on with one measurement done in our lab. The sample is a ~30nm film heat 
treated in air at 500C, composition is Ce:Sn in close to 1:1 ratio plus oxygen 
in addition to those. I can’t tell if there’s any very light elements as we 
only have EDX data at the moment, and the actual amount of O is still unclear 
due to 3-4nm of native SiO2 under the sample and I don’t have any XPS/RBS/SIMS 
profile data yet. I can’t find anything from our databases that would fit even 
remotely close to the measured data. (we have ages old PDF2 but I’ve imported 
every CeOx, SnOx and CexSnyOz structure I could find from latest ICSD). 
Indexing is a bit frustrating as well since I can’t be sure if it’s a single 
phase, and I don’t have too much experience with unknowns anyway. 
 
The measurement was done in grazing incidence mode with 1deg incident angle (it 
seems that there was some 0.014deg of 2theta shift back then).  I’ve done 
rocking curve measurements from the first six reflections, based on that it 
doesn’t seem to be textured so there shouldn’t be reflections missing due to 
that (particle statistics is obviously a different matter…). When measuring 
with different incident angles (from 0.25 to 3.75 2th) the diffractograms don’t 
seem to change, so there’s probably no separate layers but one homogeneous 
matter. The data is found here for those interesting in trying: 
http://www.helsinki.fi/~mwheikki/temp/  And before you ask, there’s no 
reflections below the one at 23.5 2th. And it’s a Cu tube.
 
I really appreciate any effort and time any of you might spend with the data. 
I’m currently trying to find something from the literature but no success so 
far. Hopefully you can make me feel stupid and find out the easy solution 
before I do J
 
Have a nice weekend!
 
BR,
Mikko
 
---
Mikko Heikkilä, M.Sc., Laboratory engineer
Laboratory of Inorganic Chemistry
Department of Chemistry
P.O. Box 55 (A.I. Virtasen aukio 1)
FI-00014 University of Helsinki
 
phone:   +358919150216
mobile:  +358504160572
email: mikko.j.heikk...@helsinki.fi
 
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Fw: [sdpd] A selection of new methods, software (or updates) for SDPD purposes since 2011

[Leonid Solovyov]

>I am sure you will list all interatomic distances soon.



No problem:
https://sites.google.com/site/ddmsuite/home/ZSM-5.cif
https://sites.google.com/site/ddmsuite/home/ZSM-5.png

Laboratory CuKa1,2 data at 200C in vacuum.
_computing_structure_refinement DDM
_refine_ls_number_parameters   112
_refine_ls_number_restraints 0
The distances and angles are listed in the CIF

Hope it is soon enough.
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



On Wednesday, October 16, 2013 8:55 PM, Armel Le Bail 
 wrote:
 
  

>Ice Age in Powder Diffraction
>Powder Diffraction Restrained in Permafrost
>Cool Powder Diffraction (CPD)

Once upon a time In Cretaceous age of powder diffraction, there was a 
Rietveld Refinement Round Robin (1989, published in 1992 and 1994). 
Of the three cases considered (PbSO4, m-ZrO2 and ZSM-5), no result 
was discussed for the latter because most participants (only 6 
recorded a pattern of the sample) concluded that this material 
contained too much crystal size broadening to permit a meaningful 
refinement of the zeolite framework structure.

You may find one of the recordings there (X-ray, CuKalpha)
http://pcb4122.univ-lemans.fr/powbase/167.zip

Quite much simple than a protein. What do you feel about it in the Ice Age ?

As a  participant, I made a fit with structure fixed which led 
already to RB~6%.
I did not dare to refine coordinates (so this is full-constraints 
which you don't like more than restrainsts I guess).

I am sure you will list all interatomic distances soon.

Best,
Armel

 open access papers :
http://scripts.iucr.org/cgi-bin/paper?gl0234
http://scripts.iucr.org/cgi-bin/paper?gl0318

Even synchrotron data were recorded of that  ZMS-5(TPA) sample, 
if someone know where to find them ?




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Re: [sdpd] Bethanechol chloride : new single crystal results

[Leonid Solovyov]

>Easy to find a lot of published restrained refinements. 
Easy to restrain, thus easy to find - nobody doubts.

>Sorry to destroy your unrestrained future.
Don't worry: even Armel Le Bail can't destroy the future.
Unrestrained refinement is possible yet for such ugly data:
http://sites.google.com/site/ddmsuite/home/dithianon_I-DDM.cif

http://sites.google.com/site/ddmsuite/home/dithianon_I-DDM.png

The precision here is much lower than in the previous example, but it might 
have been improved if the authors of that nice paper had spent more time for 
data collection and/or sample preparation.

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: s...@yahoogroups.com 
Sent: Wednesday, September 4, 2013 8:01 PM
Subject: Re: [sdpd] Bethanechol chloride : new single crystal results
 


  
Unrestrained future can't be
destroyed. Being restrained, however, it destroys
itself.
Easy to find a lot of published restrained refinements. 
Four examples in that nice 2012 paper :
http://scripts.iucr.org/cgi-bin/paper?S0108768112036191

Data available. 

No. of parameters  
106   129    260 
177
No. of restraints   
65  65   
204  139

Sorry to destroy your unrestrained future.

Best,
Armel++
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Re: [sdpd] Bethanechol chloride : new single crystal results

[Leonid Solovyov]

>
A good chemist is able to destroy any SDPD future. 

Unrestrained future can't be destroyed. Being restrained, however, it destroys 
itself.
The low-temperature single-crystal refinement doesn't eliminate the necessity 
for accurate room-temperature structural data that may be required for QPA, e. 
g.
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: s...@yahoogroups.com 
Sent: Wednesday, September 4, 2013 4:55 PM
Subject: Re: [sdpd] Bethanechol chloride : new single crystal results
 


  

>So, the unrestrained SDPD future exists and it is much more interesting.

OK, your synchrotron results are "more in agreement" with the single 
crystal ones
than my laboratory data refinement (unrestrained also...) which is 
only "in agreement".

Anyway, the unique authority is that of the single crystal result... 
The logical benefit of
non-overlapping three-dimensionnal data.

A good chemist is able to destroy any SDPD future. That 2013 good chemist was
long awaited in the bethanechol chloride case. Note that he was not 
able to obtain the
orthorhombic phase, though. so that all is not solved yet. There is 
another polymorph
clearly shown in the 2010 paper. Finally, maybe I should  try to 
solve it in spite of the
fact that it is always mixed with the monoclinic phase ? Or you 
should try. But the data
are only routine powder patterns...

Best,
Armel


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Re: [sdpd] Bethanechol chloride : new single crystal results

[Leonid Solovyov]

Dear Armel,

>From the comparison of your distances and angles with the single-crystal ones, 
>two obvious conclusions can be drawn:
1) Applying a simplified refinement model one can't expect accurate results
2) Uncertainty estimations in Rietveld programs are inadequately optimistic

Here you may see unrestrained DDM results for this structure:
http://sites.google.com/site/ddmsuite/tutorials/bethcl-DDM.cif
http://sites.google.com/site/ddmsuite/tutorials/bethcl-DDM.png
I used synchrotron data (10-years old) from:
http://sdpd.univ-lemans.fr/uppw/bethanechol.zip
The main problem was in a complex anisotropic and asymmetric peak broadening 
that you mentioned in your publication. I modeled it by including two 
pseudo-phases with variable lattice parameters.
The resulted distances and angles agree with the single-crystal ones within 3 
e.s.u.:
Single-crystal          DDM
C2 O4      1.359(4)  1.356(9) 
O4 C5      1.454(4)  1.473(7) 
O1 C2      1.217(4)  1.200(11)
C2 N3      1.338(5)  1.331(10)
C5 C6      1.521(5)  1.518(7) 
C5 C7      1.522(5)  1.530(8) 
C7 N8      1.516(4)  1.534(7) 
N8 C9      1.501(5)  1.512(7) 
N8 C10     1.496(4)  1.495(8) 
N8 C11     1.499(5)  1.491(8)
C2 O4 C5   116.6(3)  116.5(5)
O1 C2 O4   123.4(3)  123.5(7)
O1 C2 N3   125.4(3)  127.2(7)
N3 C2 O4   111.1(3)  109.3(7)
O4 C5 C6   108.1(3)  107.2(5)
O4 C5 C7   110.2(3)  109.3(5)
C6 C5 C7   109.3(3)  108.0(4)
N8 C7 C5   117.6(3)  117.1(4)
C9 N8 C7   107.3(3)  107.6(4)
C10 N8 C7  111.8(3)  110.8(5)
C11 N8 C7  112.1(3)  112.6(4)
C10 N8 C9  108.1(3)  107.8(4)
C11 N8 C9  107.3(3)  108.9(4)
C10 N8 C11 110.0(3)  109.0(4)

The C-C precision is 0.0075 A, reasonably comparable to the single-crystal 
0.005 A.
The results can be further improved if the available XRD pattern is not 
interrupted at 26.8 degrees and/or if the sample is better prepared.
So, the unrestrained SDPD future exists and it is much more interesting.

Best regards,
Leonid
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: s...@yahoogroups.com 
Sent: Tuesday, September 3, 2013 3:53 PM
Subject: [sdpd] Bethanechol chloride : new single crystal results
 


  
Hi,

For those especially interested in comparing unrestrained SDPD 
results with single crystal ones a new example is available, BC 
(bethanechol chloride) which was one of the 2003 UPPWs "Unindexed 
Powder Pattern of the Week" :
http://sdpd.univ-lemans.fr/uppw/index.html
UPPW-11 :
http://sdpd.univ-lemans.fr/uppw/uppw11.html

It was extensively used for testing various indexing sofware and 
proposed for benchmarking (2004) :
http://www.degruyter.com/view/j/zkri.2004.219.issue-12-2004/zkri.219.12.783.55862/zkri.219.12.783.55862.xml;jsessionid=5297B32E4713E27A7B5A9DAB82D2ACE6

http://sdpd.univ-lemans.fr/uppw/benchmarks/

SDPD published in 2010, restraints on H only, 298 K :
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8481214

Single crystals finally synthesized, structure published in 2013 (123 K)  :
http://pubs.rsc.org/en/Content/ArticleLanding/2013/CE/c3ce40707a

Results said to be "in agreement".

Best,

Armel Le Bail


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Re: [sdpd] Unrestrained SDPD future

[Leonid Solovyov]

As some people from the PRC reported that they can't see the files at Google 
due to Govern-Mental restrictions I put them into the SDPD-group folder:
http://tech.groups.yahoo.com/group/sdpd/files/vn2075-DDM.cif
http://tech.groups.yahoo.com/group/sdpd/files/vn2075-DDM.png

Restraints are everywhere!-) 


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Leonid Solovyov 
To: "s...@yahoogroups.com"  
Cc: "rietveld_l@ill.fr"  
Sent: Friday, August 9, 2013 2:22 PM
Subject: [sdpd] Unrestrained SDPD future
 


  
Dear colleagues,

Since the restrained SDPD future has been announced in the respective list 
without a chance to go back:
http://tech.groups.yahoo.com/group/sdpd/message/3016
It's my turn to put forward an alternative unrestrained variant that seems a 
bit more interesting and not so hopeless, IMHO.
This variant consists in a more accurate approach to the experiment and the 
modeling instead of compensating the inaccuracy by restraints.

In the discussion of the restrained Rietveld:
http://dx.doi.org/10.1107/S1600536813017522
proposed as an instance of the SDPD future trend, I presented an unrestrained 
variant of the refinement:
http://tech.groups.yahoo.com/group/sdpd/message/3023
and noted that Future improvements are possible if one exerts further efforts 
to the sample preparation, measurements and the refinement model adjustment.
Spending an extra couple of hours for the data analysis, an additional 
micro-admixture has been identified whose inclusion into the model resulted in 
further notable improvements of the structure geometry:
http://sites.google.com/site/ddmsuite/home/vn2075-DDM.cif
http://sites.google.com/site/ddmsuite/home/vn2075-DDM.png
Characteristic distances and their expectations:
Pos.    Dist.   Exp.
Co-O1  1.92(2)  1.91
Co-O2  1.94(2)  1.91
Co-N1  1.98(1)  1.96
Co-N2  1.95(2)  1.96
Co-N3  1.92(2)  1.96
Co-N4  1.99(1)  1.96
C1-O1  1.31(4)  1.32
C1-O2  1.34(4)  1.32
C1-O3  1.25(3)  1.23
N5-O4  1.27(3)  1.24
N5-O5  1.23(3)  1.24
N5-O6  1.25(3)  1.24
All distances and intramolecular angles are in agreement with the expected 
values within their uncertainties. Future improvements are still possible, 
being determined mostly by the sample preparation and measurements now.

Of course, in REALLY complex and HOPELESS cases a minimal number of constraints 
may be imposed if the refinement convergence of atomic positions is REALLY 
impossible without them. In the above example, rigid constraints were imposed 
on H-atoms, which is, though, not always necessary.

The use of soft restraints should be avoided as much as possible since a 
generally acceptable methodology of their safe application has not been 
developed yet.

Best unrestrained regards,
Leonid
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***

[Non-text portions of this message have been removed]


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++

Unrestrained SDPD future

[Leonid Solovyov]

Dear colleagues,

Since the restrained SDPD future has been announced in the respective list 
without a chance to go back:
http://tech.groups.yahoo.com/group/sdpd/message/3016
It's my turn to put forward an alternative unrestrained variant that seems a 
bit more interesting and not so hopeless, IMHO.
This variant consists in a more accurate approach to the experiment and the 
modeling instead of compensating the inaccuracy by restraints.

In the discussion of the restrained Rietveld:
http://dx.doi.org/10.1107/S1600536813017522
proposed as an instance of the SDPD future trend, I presented an unrestrained 
variant of the refinement:
http://tech.groups.yahoo.com/group/sdpd/message/3023
and noted that Future improvements are possible if one exerts further efforts 
to the sample preparation, measurements and the refinement model adjustment.
Spending an extra couple of hours for the data analysis, an additional 
micro-admixture has been identified whose inclusion into the model resulted in 
further notable improvements of the structure geometry:
http://sites.google.com/site/ddmsuite/home/vn2075-DDM.cif
http://sites.google.com/site/ddmsuite/home/vn2075-DDM.png
Characteristic distances and their expectations:
Pos.    Dist.   Exp.
Co-O1  1.92(2)  1.91
Co-O2  1.94(2)  1.91
Co-N1  1.98(1)  1.96
Co-N2  1.95(2)  1.96
Co-N3  1.92(2)  1.96
Co-N4  1.99(1)  1.96
C1-O1  1.31(4)  1.32
C1-O2  1.34(4)  1.32
C1-O3  1.25(3)  1.23
N5-O4  1.27(3)  1.24
N5-O5  1.23(3)  1.24
N5-O6  1.25(3)  1.24
All distances and intramolecular angles are in agreement with the expected 
values within their uncertainties. Future improvements are still possible, 
being determined mostly by the sample preparation and measurements now.

Of course, in REALLY complex and HOPELESS cases a minimal number of constraints 
may be imposed if the refinement convergence of atomic positions is REALLY 
impossible without them. In the above example, rigid constraints were imposed 
on H-atoms, which is, though, not always necessary.

The use of soft restraints should be avoided as much as possible since a 
generally acceptable methodology of their safe application has not been 
developed yet.

Best unrestrained regards,
Leonid
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

Thanks for
the correct citation where the term “always” is definitely absent.

A bit Better,
Leonid
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: xtal 
To: "rietveld_l@ill.fr"  
Cc: s...@yahoogroups.com 
Sent: Friday, August 2, 2013 5:25 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 

At 03:04 02/08/2013 -0700, Leonid Solovyov wrote:
> >remember the previous discussion at the
> >Rietveld list where he claimed that all H
> >can be seen and refined independently, always.
> 
> Absurd - never said so.
> From absurdity and crimes we arrived at falsifications?

Below are the unfalsified words.

Ugly yours, with pestilence,

Armel

PS- rigid brain is the first step before rigid body

=
Subject: DDM program update 1.92
Date: Sun, 16 Oct 2011 20:41:12 -0700 (PDT)
From: Leonid Solovyov 
To: rietveld_l@ill.fr

Dear Colleagues,

The DDM program update 1.92 with some minor bugs fixed is available at
http://sites.google.com/site/ddmsuite/
and
http://l-solovyov.narod.ru/ddm.html

The folder EXAMPLES\H-atoms\ now contains 15 instances of unconstrained 
refinement of H-atoms from XRPD data of various quality and complexity.

A good illustration to the recent SDPD discussion on H-atoms and restraints is 
the structure of C7H6ClN3O4S2 that was refined previously by a restrained 
Rietveld using a combination of XRD and neutron data [Acta Cryst. B (2008) 
101]. By DDM it is refined from XRD data solely without restraints including 6 
independent H-atoms [EXAMPLES\H-atoms\C7H6ClN3O4S2.ddm]. In the alternations of 
C-C and C-N distances and angles the alternations of singe and double bonds is 
correctly reproduced.
Apparently, H-atoms are not a plague and a curse, but the extensive use of 
restraints is a real disease of powder diffraction. Beside all other 
consequences, this pestilence diminishes the value of the method giving it a 
reputation of a speculative technique.

Don't restrain, be free!
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>remember the previous discussion at the 
>Rietveld list where he claimed that all H
>can be seen and refined independently, always.

Absurd - never said so.
From
absurdity and crimes we arrived at falsifications?

>Not sure that your young students have received
> a complete formation if they have to argue
>"Even Armel Le Bail has to apply restraints!".

Hope my formation is still far from completion, too.

Not the Best,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: "rietveld_l@ill.fr"  
Cc: "s...@yahoogroups.com"  
Sent: Friday, August 2, 2013 4:39 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 


>I think that Alan is right in that we should stop this thread since we 
>reach such high matters as absurdity and crime.

The end words can be the following :
Most journals have place for supplementary materials.
May be even Leonid could be happy if three tables were presented, 1- the 
raw Rietveld refinement with all parameters free, 2- results with soft 
restraints or rigid body if the author finds some magic to decide to use 
them, 3 - DFT results.

And maybe a fourth table will be required in case of the presence of H 
atoms since recently Leonid seems to recognize that DDM sometimes needs for 
fully constrain hydrogen atoms (remember the previous discussion at the 
Rietveld list where he claimed that all H can be seen and refined 
independently, always).

So, "Are restraints as good as observations ?"
Certainly not, but powder observations are so bad in complex cases that 
restraints may be admitted, and even constraints for H atoms.

Not sure that your young students have received a complete formation if 
they have to argue "Even Armel Le Bail has to apply restraints!".  Well, 
yes, even not ashamed.

Best,

Armel++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>I mean, Leonid refuse to see any reliability limit to
> the powder results. Absurdity does not exist at all
> for him (with the exception of mine apparently).
>The difference between us is that I am happy with
> 1.634(2) but already think that soft restraints are
> clearly needed when I have 1.72(3). This is all my crime...

Absurdity or credibility of results depends on the research purpose. For some 
purposes 1.72(3) may be OK if (3) is realistic, for other purposes even 
1.634(2) will be absurd especially if (2) is artificial. If you have a magic 
for a universal assessment of absurdity then this is one more "Know How" and I 
may only humbly unbonnet.

I think that Alan is right in that we should stop this thread since we reach 
such high matters as absurdity and crime.
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: s...@yahoogroups.com 
Cc: rietveld_l@ill.fr 
Sent: Friday, August 2, 2013 2:37 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 


> All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s 
> that are around 0.03 A in average.

About absurdity, there are different sensibilities...

With such a definition above, 1.72(3) instead of 1.634 is just OK for Leonid. 
Where would he see a limit before applying restraints ? Never, since he will 
find also that 1.9(1) is quite excellent, or even 2.2(3) : all deviations are 
within 3 e.s.u.s.

I mean, Leonid refuse to see any reliability limit to the powder results. 
Absurdity does not exist at all for him (with the exception of mine apparently).

The difference between us is that I am happy with 1.634(2) but already think 
that soft restraints are clearly needed when I have 1.72(3). This is all my 
crime...

Best,

Armel ++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>At the end it is all wrong as we don’t refine individual electrons
>but 
restrained groups that are called “atoms” which are 

>extrapolated with 
some average function calculated for free, 

>unbounded atom.
If you mean the scattering curves - they are not restrained, but rigidly 
constrained and these constraints are definitely and equally specified in all 
crystallographic programs, which allows comparing the refinement results and 
making reliable conclusions. In exceptional cases the scattering curves may as 
well be refined if the data permit.
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Peter Y. Zavalij 
To: Leonid Solovyov ; "s...@yahoogroups.com" 
 
Cc: "rietveld_l@ill.fr"  
Sent: Friday, August 2, 2013 6:59 AM
Subject: RE: [sdpd] Re: Are restraints as good as observations ?
 


 
At the end it is all wrong as we don’t refine individual electrons but 
restrained groups that are called “atoms” which are extrapolated with some 
average function calculated for free, unbounded atom.
 
Peter Zavalij++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>What information capacity ? The fact is that imposing
> the expected values you obtain a similar fit. This tells
> you that you cannot discuss your unrestrained "information",
> because it is unreliable.
> Information is something you may discuss reliably.
> The only possible discussion about P3-O14 = 1.72(3)A
> is to say that it is very probably strongly overestimated.

After THIS unrestrained refinement one CAN discuss RELIABLY ALL interatomic 
distances including P-O, K-O, K-P, K-K and P-P, as well as angles, orientations 
etc., WITHIN THEIR UNCERTAINTIES that are also estimated RELIABLY according to 
the EXPERIMENTALLY DETERMINED deviations of the unrestrained P-O distances. 
After the restrained refinement NOTHING can be discussed RELIABLY since neither 
the values nor their uncertainties are determined EXPERIMENTALLY.
After the unrestrained refinement one can state RELIABLY that the structure is 
DETERMINED with definite precision and, thus, discuss its features, compare it 
with other experimentally determined structures within their uncertainties, 
make more or less definite conclusions etc. After the restrained refinement one 
can only state that a hypothetical structure model is proposed and NOTHING can 
be concluded or discussed RELIABLY.
Don't you see the difference??!!
Determination = reliable experimental evaluation + reliable estimation of 
uncertainties.
Now I probably understand your "colleagues".


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: s...@yahoogroups.com 
Cc: rietveld_l@ill.fr 
Sent: Friday, August 2, 2013 12:40 AM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 


> All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s 
> that are around 0.03 A in average. Further improvements seem possible, but it 
> will require more time and efforts.
> 
> So, one more example of underestimated information capacity of powder data 
> and overestimated necessity of restraints.

What information capacity ? The fact is that imposing the expected values you 
obtain a similar fit. This tells you that you cannot discuss your unrestrained 
"information", because it is unreliable.

Information is something you may discuss reliably. The only possible discussion 
about P3-O14 = 1.72(3)A is to say that it is very probably strongly 
overestimated.

Such are powder results for complex cases.

Sure, the restrained distances cannot be discussed as well. At least they are 
not completely extravagant.

Best

Armel ++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>Leonid, I
suggest you to try K4P2O7 - synchrotron data,
>space group P61 - for which
I had to put distance restraints
>on the three P2O7 independent groups -
Powder Diffraction, 28, 2-12, 2013
  
Done
without restraints:
http://sites.google.com/site/ddmsuite/tutorials/K4P2O7-DDM.cif
Only Biso
of chemically equivalent O-atoms are constrained, while this is not absolutely
necessary.
The DDM
plot:
http://sites.google.com/site/ddmsuite/tutorials/K4P2O7-plot.png
 
Characteristic
distances:
P1-O1  1.530(30)  P2-O2  1.548(32)  P3-O7  1.536(29)  
P1-O3  1.499(26)  P2-O4  1.502(23)  P3-O9  1.481(31)  
P1-O5  1.580(28)  P2-O6  1.521(36)  P3-O11 1.542(24)  
P1-O13
1.614(30)  P2-O14 1.576(32)  P3-O14 1.719(30)  
 
P4-O8  1.552(37)  P5-O15 1.518(24)  P6-O18 1.551(31)
P4-O10
1.482(22)  P5-O16 1.553(37)  P6-O19 1.536(23)
P4-O12
1.540(34)  P5-O17 1.498(32)  P6-O20 1.486(37)
P4-O13
1.689(32)  P5-O21 1.600(28)  P6-O21 1.674(29)
 
All
deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s that are
around 0.03 A
in average. Further improvements seem possible, but it will require more time
and efforts.
 
So, one
more example of underestimated information capacity of powder data and
overestimated necessity of restraints.
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: xtal 
To: s...@yahoogroups.com; "rietveld_l@ill.fr"  
Sent: Thursday, August 1, 2013 3:10 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 


> >Leonid, I suggest you to try K4P2O7 - synchrotron data...
> 
> If you send me the data I may try.

OK.

K4P2O7 at room temperature is a good example for your horror museum of bad 
things done in the SDPD world and which could have been so much better if DDM 
was used.

This case belongs to the acentric class of problems. Acentricity leads to a 2 
times more unfavourable (atomic coordinates)/data ratio than for centric 
compounds. This is also the case for beta-Ba3AlF9 for which I can send the 
original 1993 data, if you wish, and you may see if Al-F distances are 
convincing without restraints using DDM (I obtained crazy Al-F distances in the 
1.65-1.97 A range, instead of 1.81+-0.04 A for usually regular AlF6 octahedra).

BTW, try to solve the structure before the Rietveld fif.

Best,

Armel++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>Instead,
I adopted the restraint/constraint system as soon as some
>distances
went stranges.
>Yes,
fear, fear to be personnally attacked again that way.
 
For me
restraints are much more frightful ;-(:
http://www.google.com/search?q=restraints
While for
some sort of people they may be thrilling. 
 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: xtal 
To: s...@yahoogroups.com 
Sent: Thursday, August 1, 2013 1:56 AM
Subject: Re: [SPAM] Re: [sdpd] Re: Are restraints as good as  observations ?
 


  

>Off topic : what are you afraid of ? Excuse me, but why do you use words 
>like fear ? I do not understand. Lubo

The first time some of my Le Mans "colleagues," physicists, took one of my 
SDPDs
(was beta-Ba3AlF9) and published a DFTiization of it, saying that powder 
diffraction
is close to be shit was not especially funny for me. My original paper said 
that the Al-F
distances were certainly not accurate, no restraints were appled. The 
physicists were
proud of their extraordinary success, prooving how powder diffraction 
results could be
wrong and the information was well distributed in all parts of the lab. 
Then I stopped
to deliver raw Rietveld refinement results, and stopped to say that, you 
know, this is
powder, the ratio of refined parameters/hkl is high, do not expect any 
accuracy, et(c.
Instead, I adopted the restraint/constraint system as soon as some 
distances went
stranges.

Yes, fear, fear to be personnally attacked again that way.

Better to have ennemies than such "colleagues".

Best,

Armel++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>The problem with powder diffraction measurements
> is that they often leave us information-starved.

Certain informational starvation is a feature of any experimental technique and 
powder diffraction is not a marginal one in this respect. Starvation, however, 
is not an absolution for artificial additions in natural food. Sometimes 
starvation may even help improving the health.
Sorry for the pontification if it is ;-)

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Brian Toby 
To: rietveld_l@ill.fr 
Cc: s...@yahoogroups.com 
Sent: Thursday, August 1, 2013 1:19 AM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 

Let me pontificate a bit on restraints and on R-free etc. 

The problem with powder diffraction measurements is that they often leave us 
information-starved. We just don't get enough data to investigate what we want 
to learn from the experiment, along with all the things we [think we] already 
know. No one needs to measure the flatness of a benzene ring in a 50-atom 
asymmetric unit from a powder. 

Building restraints into a model in the early stages is an excellent way to 
ensure that model stays chemically reasonable while we tinker with getting all 
the experimental terms under control. It is not unusual to have to hit the 
project over the head with restraints to make them matter (weighting them on 
the order of the number of real data points or even more). In the end it is 
nice when the weights can be set to zero, which allows us to see a fully 
relaxed fit to the data, but some problems are just too complex, even with the 
best of data. (I have a Faujasite refinement I sometimes expound upon as an 
example...). 

The way that I would describe a situation where constraints are required is 
this: the paucity of data allow a wide range of models to be fit with 
approximately the same goodness of fit. However, many of those models are not 
chemically reasonable (non-flat benzene rings for example) so we use restraints 
to make sure that we select a model that at worst is plausible. Note that even 
when we don't use restraints, almost no one ever does a uniqueness test to 
prove that their model is the only one that can fit the data and false minima 
are always possible. Every time when one looks at a published structure, with 
or without restraints, one must think that there could be another structure 
that fits the data as well, if not better. 

An important test when restraints are used is to see what happens as their 
weights are made smaller. The model may become unreasonable, since there are 
not enough data to constrain everything, but the fit to the [real] data (Rwp, 
etc.) should not get significantly better. If that is not true, then the 
restraints are in conflict with the experiment and something is wrong. 

To perform R-free with powder data, one must excise multiple complete peaks 
from the pattern, say a few sections making up 10-20% of pattern. Thus one has 
even less data. This makes the information problem above even worse. 
Macromolecular crystallographers can afford to "throw away" data because they 
fit molecular fragment envelopes, mostly not individual atoms. Sorry, no free 
lunch here. 

Brian++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>All Rietvelders (included me) are certainly trying
> a completely free refinement before to decide or
> not to use selected restraints. 

About "All" I certainly doubt.

>Am I especially scrutinized? I feel more and more
>uncomfortable about such verifications of everything I do:

I believe that one should be happy about such an interest to his works ;-)

>Leonid, I suggest you to try K4P2O7 - synchrotron data...

If you send me the data I may try.

Regarding the fears, the colleagues etc.: geometric and other parameters can 
not be regarded as wrong or right irrespectively of their uncertainties. If 
distances deviate from their expectations or DFTized values within 3 e.s.u. 
they are not wrong - they are REAL (if e.s.u. are real).

***

Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Armel Le Bail 
To: rietveld_l@ill.fr 
Cc: s...@yahoogroups.com 
Sent: Wednesday, July 31, 2013 11:48 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 


>The problem of having jammed
the wrong molecule
>> into a unit cell can be identified by restraints which
>> are violated. With rigid bodies it is more difficult to
>> find out what the data are trying to tell you. Is this 
>>wrong molecule issue the problem you fear?
>
>I prefer resolving such problems by unrestrained refinement with minimal
rigid constraints on unambiguous parts which can't be
refined.
All Rietvelders (included me) are certainly trying a completely free
refinement before to decide or not to use selected restraints. I tried,
and finally preferred to use some soft restraints (the fear of being
DFTized because of some interatomic distances obviously out of their
usual range). Some of my old SDPDs without restraints were DFTized, the
DFTizers were claiming that powder results are good for some dustbin...
Now I am guilty according to Leonid (guilty to not use DDM working so
much better than Fullprof in such cases; dur to the so clever background
treatment)... But the paper was accepted ;-). A few days after I received
a DFTization... Am I especially scrutinized ? I feel more and more
uncomfortable about such verifications of everything I do (Leonid, I
suggest you to try K4P2O7 - synchrotron data, space group P61 - for which
I had to put distance restraints on the three P2O7 independent groups -
Powder Diffraction, 28, 2-12, 2013) !

Are all my results so bad ? Below is the COMPSTRU Bilbao software output
of the comparison of the calcium glycinate trihydrate as published in
Acta C and as from the Leonid DDMization with contraints "only"
on H atoms (a lot of constraints BTW, there are 14 independent H
atoms...). The measure of similarity is 0.027. We will have to wait for
the single crystal results (if any some day) before to conclude to the
best way to proceed in that case. Anyway, if the molecule is wrong, it is
wrong in both powder refinements.

Armel++
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++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>Likelihood and/or the free R-factor offer routes to choose restraint 
>weights...


I don't exclude a potential possibility for an efficient, reasonable and 
profitable application of even such dirty tricks as soft restraints. Also I'm 
sure that a hypothetical opportunity exists for a method of choosing most 
robust and safe weights of restraints. Yet all these requisites are not 
observed in the current SDPD practice.


>I'm not against constraints, but how do you go about validating somebody 
>else's choice of rigid definition?


Validation is a manifold issue similarly complex both for softly-restrained and 
for free+constrained refinement. Fortunately, some positive practice has been 
developed in the "last ~100 years of crystallography" using rigid-body 
fragments.

 
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Jonathan WRIGHT 
To: s...@yahoogroups.com 
Cc: Leonid Solovyov ; "rietveld_l@ill.fr" 
 
Sent: Wednesday, July 31, 2013 11:36 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 

On 31/07/2013 17:25, Leonid Solovyov wrote:
> One can make everything "OK" simply by choosing an "appropriate" weight
> of restraints. The uncertainty in the restraint's weight appropriateness
> makes every restrained refinement a "know how".

Likelihood and/or the free R-factor offer routes to choose restraint 
weights, see eg:

http://www-structmed.cimr.cam.ac.uk/Course/Likelihood/likelihood.html#restraints
http://people.cryst.bbk.ac.uk/~tickle/rfree/paper.html

Regardless of the weighting chosen, the weighted difference which comes 
back (per restraint) tells you what the data think about the restraint 
target value. This information could be deposited along with the fit to 
the powder data for all to see.

I'm not against constraints, but how do you go about validating somebody 
else's choice of rigid definition?

Cheers,

Jon++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: [sdpd] Re: Are restraints as good as observations ?

[Leonid Solovyov]

>input restraint: C(sp3) to C(sp3) distance ~ 1.54
>output distance: 1.54 -> OK
>output distance: 1.4x -> Could it be sp2-sp2 or a wrong atom assignment?

One can make everything "OK" simply by choosing an "appropriate" weight of 
restraints. The uncertainty in the restraint's weight appropriateness makes 
every restrained refinement a "know how".

>So, assuming your restraints are correct for your sample
>then you are adding information into your refinement.
>This causes the rest of the results to improve as you
>reduce the noise in the output.

This is definite for the restrained part only. For the rest it depends.

>Structure refinement is not likely to work out if you can't
>fit the peak shape or have unidentified impurities or unfitted
>texture texture etc.

The restrained refinement "works" even in worse cases as is "proved" by the 
modern practice.

>It does not make sense to have the atomic
> positions soaking up systematic problems.

This soaking up is, unfortunately, unavoidable both with and without 
restraints. If you tread out systematic problems from the restrained part they 
are likely to concentrate in the rest. 

>The problem of having jammed the wrong molecule
> into a unit cell can be identified by restraints which
> are violated. With rigid bodies it is more difficult to
> find out what the data are trying to tell you. Is this 
>wrong molecule issue the problem you fear?

I prefer resolving such problems by unrestrained refinement with minimal rigid 
constraints on unambiguous parts which can't be refined.

>TL;DR: Garbage in garbage out. OK. 
>What has that got to do with restraints?

Pouring a glass of distilled water in a garbage-can doesn't make it cleaner. 

Neither my experience nor this discussion can convince me that soft restraints 
are better than free refinement with minimal rigid constraints, and I'm not the 
only one [A. Immirzi, Constraints and restraints in crystal structure analysis, 
J. Appl. Cryst. (2009) 362].
Nevertheless, I'm not totally against these tricks if they are applied properly 
as exceptions (not as a rule), and if the uncertainties of the results are 
estimated realistically. The current SDPD practice, however, consists mainly in 
the opposite.
 

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***



 From: Jonathan WRIGHT 
To: Leonid Solovyov  
Cc: "s...@staffmail.ed.ac.uk" ; "rietveld_l@ill.fr" 
; "s...@yahoogroups.com"  
Sent: Wednesday, July 31, 2013 7:48 PM
Subject: Re: [sdpd] Re: Are restraints as good as observations ?
 

On 31/07/2013 03:07, Leonid Solovyov wrote:
> ...  There is a
> widely scattered belief that restraints always improve not only the
> restrained values, but also the “unrestrained” part of structure such as
> intermolecular distances, orientations, planarity etc.

Apart from your word "always", I certainly believe restraints can and should 
improve the unrestrained output from Rietveld refinements. A couple of points:

1) You should be checking whether the restraint target value is consistent with 
the experimental data by looking at whether it comes back at the end of the 
refinement. For example:

input restraint: C(sp3) to C(sp3) distance ~ 1.54
output distance: 1.54 -> OK
output distance: 1.4x -> Could it be sp2-sp2 or a wrong atom assignment?

An outlier in the fit to your restraints is just as much as a problem as an 
outlier in the fit to your data. You should be looking at the difference/esd, 
where the esd was also input.

2) If you are terribly worried what restraints are doing then you might like to 
look into "Rfree" statistics. It would be cool for them to make it into some 
mainstream Rietveld software (doi:10.1524/zkri.219.12.791.55857, or 
doi:10.1038/nature12070).

So, assuming your restraints are correct for your sample then you are adding 
information into your refinement. This causes the rest of the results to 
improve as you reduce the noise in the output.

> ...  The general
> practice, however, consists in applying restraints in the cases of
> highly biased reflection intensities and peak shape misfits when the
> residuals are strongly correlated. In such cases restraints compensate
> the influence of misfits on the restrained values at the expense of
> their increased influence on the “unrestrained” part.

The restraints should improve the model, if they don't, see above. Getting one 
part of a model right makes it easier to find out what is missing to get the 
whole thing (about) right. If there are serious misfits this means there

DDM-GUI beta version

[Leonid Solovyov]

Dear All,

A beta-version of GUI for the Derivative Difference Minimization program DDM is 
available from
http://sites.google.com/site/ddmsuite
and
http://www.icct.ru/eng/content/persons/Sol_LA/ddm.html

Many thanks to Alexandr Zaloga, Yaroslav Yakimov and Igor Yakimov from the 
Siberian federal university for their work!

The program will be developed further and your suggestions, bug reports and 
comments are cordially welcome.

The main changes in DDM 1.8 are:
1. The atomic dispersion and attenuation coefficients for the wavelength range 
0.124 - 3.1 A (with all absorption edges) are included
2. An automatic microabsorption contrast correction is added
3. The ellipsoidal preferred orientation correction may be applied together 
with a uniaxial one

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***



  

Re: Microstructural analysis by fullprof

[Leonid Solovyov]

Dear Alice,

The Gaussian component may be related to either the instrumental broadening or 
a narrow crystal size distribution. In the case you described I see two 
possible options:
1) You don’t properly take into account the instrumental contribution which is 
most pronounced for big crystallites.
2) For your samples the size distribution of big crystallites is narrower and 
you have to include the Gaussian component.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***


--- On Fri, 2/19/10, Alice Courleux  wrote:

> From: Alice Courleux 
> Subject: Microstructural analysis by fullprof
> To: rietveld_l@ill.fr
> Date: Friday, February 19, 2010, 1:34 PM
> Dear Rietvelders,
> 
> I am using Fullprof  to microstructural analysis of
> particles. I have one type of particle but different sample
> with different sizes (particles increase after heat
> treatment). Their crystallites size fluctuates between 10nm
> and 1µm. I know that 1µm is big for a refinement Rietveld.
> To calculate the size, I refine Y (Lorentzian componant)
> then Ig (Gauss component).
> If the crystallites are small (<20nm) I can only refine
> the Y parameter. If I try to refine Ig, I have a error
> message "negative Gaussian parameter" and no crystallites
> size.
> For bigger crystallites, I can refine Y and Ig. If I only
> refine Y, the crystallite size is smaller than the size with
> Y and Ig refinement.
> For the biggest crystallites if I only refine Y parameter
> the size is "9nm". However if I refine Ig parameter too,
> I  succeed to have a size (1300nm for example)...
> I don't understand why I can't refine Ig whatever the 
> crystallites size... Is ther any reason to that?
> Should I only refine Y for all my samples? Or refine Y and
> Ig when it's work and only Y when Ig bugs?
> Have you ever seen this problem?
> 
> Thanks a lot for your  help.
> 
> Best regards,
> 
> Alice
> 
> -- Laboratoire des Multimatériaux et Interfaces - CNRS UMR
> 5615
> Université Claude Bernard Lyon 1
> 3ème étage - Bâtiment Berthollet
> 43, boulevard du 11 Novembre 1918
> 69622 VILLEURBANNE Cedex
> 
> Mail: alice.courl...@univ-lyon1.fr
> Tél: 04.72.43.12.34
> 
> 
> 


  

Re: calcul of a vector indices

[Leonid Solovyov]

Dear Teresa,

The nearest Miller indexes of planes in Mercury are displayed in
Display -> More information -> Planes list

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***

--- On Fri, 1/15/10, Mª Teresa Calvet  wrote:

> From: Mª Teresa Calvet 
> Subject: calcul of a vector indices
> To: rietveld_l@ill.fr
> Date: Friday, January 15, 2010, 4:19 PM
> 
> 
>  
>  
> 
> 
>  
> 
> Dear all,
> I need to calculate the indices 
> of Miller of a vector that corresponds to a direction of
> interactions between 
> molecules of a structure (I have de cif
> file).
> 
>   
> Can somebody recommend a program 
> to me that selecting the atoms can calculate the vector
> indices?  I have tried with Mercury but it
> only 
> calculates planes. 
>  
> Thanks for your help.
> Regards
> Teresa Calvet
>  
> 
> 


  

RE: Configuration of PANalytical X'pert Pro

[Leonid Solovyov]

Dear Alexandra,

The 1/4 divergence and 1/2 anti-scatter slits are narrow enough to give a 
reasonably low background after 5 degrees 2Theta. First I would check that the 
background is not related to the sample itself. It may be done by measuring an 
empty sample holder.
The background may also be due to scattering from sample holder edges if the 
holder diameter is small and the primary beam mask is wide or/and the Soller 
slit divergence is big.
The automated sample changer can not produce background, but I am not sure if 
the beam knife can be installed together with the changer. The beam knife cuts 
the air scattering which is essential in the low-angle region. The standard 
beam knife supplied by PANal is rather thick and if it is installed too close 
to the sample surface it may attenuate intensity at high angles. With fixed 1/4 
divergence slit the knife should be put about 3-4 mm under the sample surface 
which must be safe for measurements up to 100 degrees 2Theta. To check if the 
knife attenuates high angle reflections it is necessary to measure the same 
sample with and without knife and then compare the intensities.
On my X’Pert I simply replaced the standard knife by a thin (ca. 1 mm) 
stainless steel screen,  and installed it 3 mm above the sample surface which 
allows preserving intensity up to 150 degrees 2Theta even with the 1/2 
divergence primary slit and have a reasonable low-angle background. Of course, 
the knife should also be properly centered on the diffractometer axis and 
aligned vertically.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***

--- On Mon, 11/30/09, Alexandra Seclaman  wrote:

> From: Alexandra Seclaman 
> Subject: RE: Configuration of PANalytical X'pert Pro
> To: rietveld_l@ill.fr
> Date: Monday, November 30, 2009, 2:05 PM
> Thank
> you for all of your answers, it was more than I hoped for. 
> 
> I did a Rietveld refinement on stibnite (Sb2S3). And I
> mesured it from 5 2theta to 90. But  from 5 to 20 2Θ i
> had a serious background noise and general trend similar to
> that of glass. This trend and the background noise are there
> no matter what I measure. 
> I can't get to the lab until Wednesday, but from what I
> recall, from the X ray source to the X'celerator
> detector: there are 1/4 +1/2 fixed divergence,the widthest
> mask and the slit (i'm not shure if that is the proper
> name) in front of the X'celerator is also the widthest.
> 
> The automated system of "handling" the sample is
> installed, should i changed it? 
> And I forgot to mention, the system is MPD. 
> 
> I can give you more details on Wednesday.  
> 
> I'm sorry for my not technical terms, but is very hard
> for me
>  to speak about diffraction in English. 
> 
> 
> Alexandra Seclaman
> 
> seclaman_alexan...@yahoo.com
> 
> a.c.secla...@gmail.com
> 
> --- On Sun, 11/29/09, Tony Raftery
>  wrote:
> 
> From: Tony Raftery 
> Subject: RE: Configuration of PANalytical X'pert Pro
> To: "Alexandra Seclaman"
> 
> Date: Sunday, November 29, 2009, 11:57 PM
> 
> Alexandra,
> 
> while there is no such thing as a standard configuration,
> choices can be made to help in the modelling. Another
> corresponant (to the Rietveld list)  made some
> suggestions that I only partly agree with. A lot depends on
> you goals ans available instrumentation - for instance if
> you have an X'cellerator detector and a monochromator.
> If you are interested in the low angle region (as I think
> you are) or not. If you were looking at some phases or
> phases where the peaks began after
>  25 deg 2theta, you could afford to go to larger divergence
> than if the peaks started at 5 deg 2theta.
> 
> I see little use for beam knifes except over restricted low
> angle ranges (they always interfere at high angle, where
> they interfere depends on how they are set). It see little
> use for varable divergence slits for all sorts of reasons
> (firstly as there is no rock solid conversion from automatic
> to fixed intensities, secondly the resolution changes with
> angle with variable slits that can't be modelled -
> unless a more sofisticated model than that of Highcore Plus
> is used).
> 
> What I agree with is that you need to use and properly
> adjust the anti-scatter slits.
> 
> Fro memory (I am away from the lab for a few weeks) my
> conditions are for scans 3.5 deg to 140 deg 2theata - a
> general scan, well crystalled phases
> fixed divergence 0.5 deg, a-scatter (incident) 1 deg,
> sollers (incident) 0.04 rad
> 3.4mm (diffracted) a-scatter, mono fot
>  X'cellerator, X'cellerator set full )about 2 deg)
> step 0.02 deg (or what X'cellerator allows, in my case
> 0.0167 deg), step-time to give about 10,000 counts full
> scale
> 
> F

Re: Configuration of PANalytical X'pert Pro

[Leonid Solovyov]

Dear Alexandra,

The term “standard configuration” is rather indefinite since PANal has a lot of 
various configurations and accessories. The most straightforward option for 
reducing the low-angle background is the programmable divergence and 
anti-scatter slits. For a fixed slit system the low-angle background may be 
reduced by primary slits and mask of lower divergence and a proper adjustment 
of the beam knife (above the sample) that cuts the air scattering. The 
alignment of the sample holder in the primary beam is also important for 
low-angle measurements.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***

--- On Fri, 11/27/09, Alexandra Seclaman  wrote:

> From: Alexandra Seclaman 
> Subject: Configuration of PANalytical X'pert Pro
> To: "rietveld_l@ill.fr" 
> Date: Friday, November 27, 2009, 5:09 PM
> Hello,
> 
> 
> 
> 
> 
> 
> I have done a Rietveld refinement using a PANalytical
> X'pert
> Pro but the standard configuration is giving me a lot of
> troubles. This
> configuration is somewhat "blind" to the small 2
> theta angles and it
> introduces (because of the poorly focused X ray beam) a
> heavy
> background. I've manage to remove that background by
> refinement but I'm
> sure that the quality of the acquisition can be
> improved.  
> 
> I am no engineer, so the inner workings of that machine are
> somewhat a
> mystery to me. I am asking if someone else has used a
> PANalytical for
> Rietveld and if you can give me a better configuration of
> slots, masks
> etc. I have tried different configurations with no
> success.
> 
> 
> 
> 
> Please take into consideration, while writing your reply,
> that I'm still a student and I have yet a lot to learn. 
> 
> 
> 
> 
> 
> Thank you!
>
> 
> 
> Alexandra Seclaman
> 
> seclaman_alexan...@yahoo.com
> 
> a.c.secla...@gmail.com
> 
> 
>   


  

Re: [No subject]

[Leonid Solovyov]

Dear Dave,

Again, without data it is difficult to say what is right or wrong…
I see that you did not refine the LY parameters responsible for strain 
broadening. It means that you neglect the microstrain effect which is hardly 
reasonable especially for ball-milled samples.

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***

--- On Wed, 11/11/09, David Weston  wrote:

> From: David Weston 
> Subject: 
> To: Rietveld_l@ill.fr
> Date: Wednesday, November 11, 2009, 3:50 PM
> Dear All,
> 
> I have taken the LaB6 instrumental data supplied by Leonid
> Solovyov
> (Many thanks!) and I have used it for a heavily milled MgH2
> powder.  The
> MgH2 is contaminated with stainless steel from the milling
> pot/balls and
> a bit of oxide.  I have allowed the LX parameter to
> vary.  The results
> are attached.   I would be grateful if
> someone would supply any
> constructive comments please.  (Have I got this
> right?)
> The MgH2 pattern is as measured.  i.e. no stripping of
> Kalpha2, and it
> has not been smoothed (which a previous version was!)
> 
> I am told we do have Soller slits on the machine and will
> look into how
> effective they are at the moment.  
> 
> I would like to say how very much I appreciate the help
> which has been
> vital to me getting moving with this technique.
> 
> Best Regards
> 
> Dave Weston 
> Research Fellow
> Department of M3 
> Wolfson Building
> University of Nottingham
> 



  

Re:

[Leonid Solovyov]

Dave,

If you can send also the data-file you may increase a chance to get further 
feedback.

Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
sites.google.com/site/solovyovleonid
***

--- On Thu, 11/5/09, David Weston  wrote:

> From: David Weston 
> Subject: 
> To: Rietveld_l@ill.fr
> Date: Thursday, November 5, 2009, 5:37 PM
> OK
> 
> I have gone to CW4 and got this.  The peak shapes are
> much better than
> before.  Thanks very much! But I don't seem to be able
> to improve this
> any further.  Any ideas please?
> 
> Dave Weston 
> Research Fellow
> Department of M3 
> Wolfson Building
> University of Nottingham
> 
> This message has been checked for viruses but the contents
> of an attachment
> may still contain software viruses, which could damage your
> computer system:
> you are advised to perform your own checks. Email
> communications with the
> University of Nottingham may be monitored as permitted by
> UK legislation.
> 
> 


  

Re: Rietveld Neophyte

[Leonid Solovyov]

Dear Dave,

Actually, GSAS is not the best choice for crystal size analysis. There are 
specialized programs for this purpose such as MAUD for instance.

If you can’t refine the Gaussian broadening parameters GU GV and GW you may get 
them from the refinement for a standard with big (>1000 nm) crystallites in 
order to allow for the instrumental broadening. Then you should refine not only 
LX, but also LY parameter responsible for the strain broadening. If you are 
lucky enough to refine LX without strong correlations with LY, background and 
other parameters, you may get an estimation of the crystallite size from the 
expression given in chapter ‘Interpretation of CW powder profile coefficients’ 
of GSAS manual. However, for “horrible data with very broad peaks of very low 
intensity” you may get misleading results due to incorrect separation of size, 
strain, and instrumental broadening contributions.

Best regards,
Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 sites.google.com/site/solovyovleonid
***

--- On Fri, 10/23/09, David Weston  wrote:

> From: David Weston 
> Subject: Rietveld Neophyte
> To: Rietveld_l@ill.fr
> Date: Friday, October 23, 2009, 10:27 AM
> 
> Hello,
> 
> I have been using the GSAS software to analyse some XRD
> data from MgH2
> samples that have been heavily milled.  
> One piece of information I would like to assertain is the
> mean particle
> size of my powders.  The powders are of the order of
> 10 nm by TEM.  
> Some relevant information;
> I am using a type 2 profile function.
> My data is horrible with very broad peaks of very low
> intensity.  
> I have had to set the GU GV and GW parameters in order to
> do anything at
> all. If I let them float then I lose any semblance.  
> I get a Chi2 < 1.
> 
> My question is this;
>     How do I obtyain the particle
> size?  
> 
> Is it the LX parameter and is this measured in Angstroms?
> 
> I hope someone will be kind enough to help me out of this
> mire!
> 
> Regards
> 
> Dave Weston 
> Research Fellow
> Department of M3 
> Wolfson Building
> University of Nottingham
> 



  

Re: Asymmetry profile

[Leonid Solovyov]

Dear Alex,

Quartz is not the best standard for the instrumental asymmetry determination 
since it does not have low-angle peaks. So, if you fixed the asymmetry 
parameter to that determined for quartz you may have problems in the low-angle 
area.
It is always better to refine the asymmetry parameter as it is not only 
instrument-dependent but also sample-dependent. The asymmetry may depend on the 
absorption coefficient, the powder packing density, the capillary diameter and 
other parameters.

Best regards,
Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Tue, 8/11/09, Alex Sinclair  wrote:

> From: Alex Sinclair 
> Subject: Asymmetry profile
> To: rietveld_l@ill.fr
> Date: Tuesday, August 11, 2009, 12:09 PM
> 
> 
> 
> #yiv1270810026 .hmmessage P
> {
> margin:0px;padding:0px;}
> #yiv1270810026 {
> font-size:10pt;font-family:Verdana;}
> 
> 
>  
> Dear mailing
> list,
>   
> Would anyone
> be able to help me with a problem I am having refining some
> data using TOPAS on a lab X-ray pattern?
>   
> The
> diffraction patterns collected show a large amount of
> asymmetry in the first couple of (low angle)
> peaks.
>   
> The
> diffractometer contribution to the profile was determined
> from refinement of a quartz standard and the sample
> dependent broadening was then modelled using the PV-II
> function within TOPAS. Axial convergence parameters were
> used to model the angle-dependent asymmetry.
>  
> Unfortunately the asymmetry of the first, lowest
> angle peak is still being fitted very poorly. Are there any
> other parameters or tricks that will help to model this
> asymmetry?
>   
> Many thanks
> for any help you have,
> Alex
> 
>   
> P.S.
> Additionally, the data was collected using a Bruker D8
> Advantix diffractometer in capillary geometry, with a Cu
> source, a Ge(111) monochromator, secondary soller slits (2.5
> degrees) and an linear PSD. 
> Celebrate
> a decade of Messenger with free winks, emoticons, display
> pics, and more. Get
> Them Now 
> 


  

Re: LP factor in the Rietveld refinement

[Leonid Solovyov]

Thanks, Nicolae, for the didactic comment, but I must add that the expression

pol = SIN(PSI)**2 + COS(PSI)**2*COS(2*TET1)**2*COS(2*TET2)**2 
*.*COS(2*TETm)**2*COS(2*TETb)**2

is an idealization and the real polarization factor may deviate notably from 
the idealized one depending on the crystal type (perfection/mosaicity) and 
other factors especially for multi-bounce systems. So, regarding the 
polarization factor of a real system in use, it is better to either consult the 
manufacturer or try determining it experimentally, for example, by measuring 
the same standard sample with and without monochromator.

Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Mon, 7/27/09, Nicolae Popa  wrote:

> From: Nicolae Popa 
> Subject: Re: LP factor in the Rietveld refinement
> To: "Leonid Solovyov" , rietveld_l@ill.fr
> Date: Monday, July 27, 2009, 11:04 AM
> Right, but specially for students-
> beginners we must  be much, let say, didactic
> 
> LP means (Lorentz) * (Polarisation)
> What is important in Rietveld refinement when a lot of
> mirrors & monochromators are present is how they change
> (Polarization)
> because (Lorentz) is changed by adding factors independent
> on hkl, then entering in the scaling factor
> 
> Presuming the same scattering plane for all "scatterers"
> the polarization factor is:
> 
> 
> pol = SIN(PSI)**2 +
> COS(PSI)**2*COS(2*TET1)**2*COS(2*TET2)**2
> *.*COS(2*TETm)**2*COS(2*TETb)**2
> 
> 
> where   TET1, TET2, .,
> TETm   are the Bragg angles at monochromator
> 1, 2, ,m
> 
> and where  TETb  is the Bragg angle at 
> sample  (depending on hkl)
> 
> and where PSI  is the angle between polarization 
> vector of the incident beam - IF it is TOTALLY POLARIZED!!!
> - and the scattering plane;
> 
> If the incident beam is NOT POLARIZED the averages of both
> SIN(PSI)**2 and COS(PSI)**2  result in 1/2.
> 
> If the incident beam is partially polarized one replace for
> example SIN(PSI)**2  by  P0 , consequently
> COS(PSI)**2 = 1 - P0  and one refine P0
> 
> If the geometry is much complicated (different scattering
> planes for different monochromators) "pol" should be
> calculated for the given
> 
> geometry  by applying successively the known formula
> (see a book of electrodynamics, e.g.. Landau)
> 
> Ej+1 = (Ej X u)Xu  and taking at the END: 
> |E(last)|**2 / |E0|**2     (X means
> vectorial product)
> 
> where Ej is the electric field vector in the beam scattered
> j times and  u is the unit vector along the scattered
> beam j+1
> 
> Best wishes,
> 
> Nicolae Popa
> 
> 



  

RE: LP factor in the Rietveld refinement

[Leonid Solovyov]

In principle, the LP correction for a multi-bounce monochromator is similar to 
that for a single-crystal one with the same crystal type and reflection indexes 
(or diffraction angle).
The exact LP value depends, as well, on the crystal perfection (mosaicity) and 
for supremely precise measurements one might consider refining the LP value as 
was mentioned by Kurt and Peter. Besides the angular range, the correlation 
with thermal parameters, and the instrument alignment, one more problem of the 
LP refinement is the correct choice of the atomic scattering curves in 
accordance with the oxidation states which might be not quite obvious in 
general.

Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Sun, 7/26/09, Peter Y. Zavalij  wrote:

> From: Peter Y. Zavalij 
> Subject: RE: LP factor in the Rietveld refinement
> To: rietveld_l@ill.fr
> Date: Sunday, July 26, 2009, 5:03 AM
> That's right. LP refinement works
> just fine within TOPAS but angular range
> as wide as possible is needed. If it is up to 140-150 deg.
> 2thteta LP does
> not correlate much with thermal parameters. Refined LP is
> not exact but very
> close.
> 
> Peter Zavalij 
> 
> X-ray Crystallographic Center
> University of Maryland
> College Park, MD
> 
> Office: (301)405-1861
> Lab: (301)405-3230
> Fax: (301)314-9121
> 
> 
> 
> 
> -Original Message-
> From: Kurt Leinenweber [mailto:ku...@asu.edu] 
> Sent: Saturday, July 25, 2009 8:53 PM
> To: alor...@unex.es;
> Leonid Solovyov
> Cc: rietveld_l@ill.fr
> Subject: RE: LP factor in the Rietveld refinement
> 
> Hi all,
>  
> I haven't actually DONE this, so maybe I shouldn't put my 2
> cents in, but
> can't you refine the polarization factor by using a
> standard such as Y2O3
> and fixing the structure and thermal parameters of the
> standard while
> refining the polarization angle?
>  
> The angle so obtained should agree with what the theory
> tells you for your
> diffractometer configuration, but it seems more comforting
> to verify it by a
> measurement.
>  
> - Kurt
> 
> 
> 
> From: alor...@unex.es
> [mailto:alor...@unex.es]
> Sent: Sat 7/25/2009 1:29 PM
> To: Leonid Solovyov
> Cc: rietveld_l@ill.fr
> Subject: Re: LP factor in the Rietveld refinement
> 
> 
> 
> In this context:
> 
> What about the LP for a Goebel mirror followed by a
> 4-bounce or 2-bounce
> primary monochromator?
> 
> Best regards
> 
> angel l. ortiz
> 



  

Re: LP factor in the Rietveld refinement

[Leonid Solovyov]

As far as I know, for X-ray mirrors the LP angle is near zero.

Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Sat, 7/25/09, chu...@hkusua.hku.hk  wrote:

> From: chu...@hkusua.hku.hk 
> Subject: Re: LP factor in the Rietveld refinement
> To: "Ross H Colman" 
> Cc: rietveld_l@ill.fr
> Date: Saturday, July 25, 2009, 4:16 AM
> Dear Ross,
> 
> How about the LP factor/monochromator angle if using Gobel
> mirror in  
> my D8 system?
> 
> Thanks!
> 
> stephen
> 
 


  

Re: AW: LP factor in the Rietveld refinement

[Leonid Solovyov]

The surface roughness effect depends on both the roughness and the absorption 
coefficient, and for LaB6 it may be notable if the sample surface is really 
rough. However, this effect leads to a systematic DECREASE of the LOW-ANGLE 
reflections which seems to be not the case since the correction with LP=90 
works conversely.

Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Thu, 7/23/09, David Lee  wrote:

> From: David Lee 
> Subject: Re: AW: LP factor in the Rietveld refinement
> To: "Reitveld" 
> Date: Thursday, July 23, 2009, 2:19 PM
> I have a question about the surface
> roughness.    The LaB6 powders that I have seen
> are
> very finely ground and produce very flat, smooth
> samples.     Is the roughness connected
> with the absorption?   I'm thinking along
> the lines that a low absorbing, rough sample
> might not "look" as rough to an x-ray beam as a high
> absorbing, smoother sample.
> 
> Thanks,
> 
> David Lee, Ph.D.
> DTLee Scientific, llc
> http://www.dtlee.com
> 614-562-6230
> 
> On Jul 23, 2009, at 5:23 AM, Hinrichsen, Bernd wrote:
> 
> > One intensity correction that is perhaps more
> realistic is surface roughness. This does have a vaguely
> similar angular dependence to the LP correction. This
> correction is generally only applied to highly absorbing
> samples in Bragg-Brentano (or generally reflection) setups.
> This would seem to be the case for the LaB6 measurement
> mentioned by Peter.
> > 
> > Greetings
> > Bernd
> > 
> > 
> > -Ursprüngliche Nachricht-
> > Von: Peter Y. Zavalij [mailto:pzava...@umd.edu]
> > Gesendet: Donnerstag, 23. Juli 2009 05:52
> > An: rietveld_l@ill.fr
> > Betreff: RE: LP factor in the Rietveld refinement
> > 
> > Well... the situation with LP is not so simple. Using
> TOPAS for refinement
> > data collected on D8 advance with Ni-filter and
> LynxEye detector I observe
> > the following:
> > - For all samples LP=0 is OK and gives the best fit as
> it should be by the
> > book.
> > - HOWEVER for LaB6 standard LP=0 yields very poor fit
> for several high angle
> > reflections (>120 deg. 2theta) while LP=90 gives
> perfect fit. The difference
> > in R factors 12% and 4% cannot be simply ignored...
> > 
> > Can anyone explain this?
> > 
> > 
> > Peter Zavalij
> > 
> > X-ray Crystallographic Center
> > University of Maryland
> > College Park, MD
> > 
> > Office: (301)405-1861
> > Lab: (301)405-3230
> > Fax: (301)314-9121
> > 



  

RE: LP factor in the Rietveld refinement

[Leonid Solovyov]

Dear Angel,

In general, the LP correction angle is the diffraction angle (2theta) of the 
monochromator crystal. If the primary monochromator is Si(111) then the angle 
is 28.44 for CuK_alpha1.

Best regards,
Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Thu, 7/23/09, alor...@unex.es  wrote:

> From: alor...@unex.es 
> Subject: RE: LP factor in the Rietveld refinement
> To: "Leonid Solovyov" 
> Cc: rietveld_l@ill.fr
> Date: Thursday, July 23, 2009, 7:00 AM
> Dear All,
> 
> In this scenario, which should be the number for LP in
> Topas if ones has a
> D8 with a primary monochromator for pure CuKalpha1?
> 
> thanks for the response,
> 
> angel l. ortiz
> 



  

RE: LP factor in the Rietveld refinement

[Leonid Solovyov]

Dear Peter,

Of course the LP correction can't be sample-dependent and for your 
configuration LP=0 should be Ok for all samples. It seems that you have an 
intensity loss at high-angles that may be partly compensated by LP=90. Possible 
reason may be in a misalignment of the anti-scattering slits or screen (knife) 
if you use them.

Best regards,
Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk , Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***

--- On Thu, 7/23/09, Peter Y. Zavalij  wrote:

From: Peter Y. Zavalij 
Subject: RE: LP factor in the Rietveld refinement
To: rietveld_l@ill.fr
Date: Thursday, July 23, 2009, 4:52 AM

Well... the situation with LP is not so simple. Using TOPAS for refinement
data collected on D8 advance with Ni-filter and LynxEye detector I observe
the following: 
- For all samples LP=0 is OK and gives the best fit as it should be by the
book.
- HOWEVER for LaB6 standard LP=0 yields very poor fit for several high angle
reflections (>120 deg. 2theta) while LP=90 gives perfect fit. The difference
in R factors 12% and 4% cannot be simply ignored...

Can anyone explain this?


Peter Zavalij 

X-ray Crystallographic Center
University of Maryland
College Park, MD

Office: (301)405-1861
Lab: (301)405-3230
Fax: (301)314-9121



  

Re: about background substraction

[Leonid Solovyov]

Dear Wahyu,

You may do quantitative analysis without background refinement or subtraction 
using DDM:
www.icct.ru/Eng/Content/Persons/Sol_LA/ddm.html

Regards,
Leonid


--- On Tue, 5/19/09, wahyu bambang  wrote:

From: wahyu bambang 
Subject: about background substraction
To: "rietveld_l" 
Date: Tuesday, May 19, 2009, 11:16 AM

Dear all rietvelder,

Please give me a suggestion about my problem.
I want to do quantitative analysis using GSAS, however my diffraction
pattern has very high and rough background which makes me difficult to
do preliminary qualitative works to determine the available phases.

Is it alright if I substract the background and refine it a little
first using another refinement software before I go through GSAS?

I really appreciate your kindness to answer.

regards,

wahyu



  

DDM update 1.7

[Leonid Solovyov]

Dear All,

A new version (1.7) of the Derivative Difference Minimization program DDM is 
available at:
www.icct.ru/Eng/Content/Persons/Sol_LA/ddm.html
mirrors:
l-solovyov.narod.ru/ddm.html
www.geocities.com/l_solovyov/ddm.html

The main changes:
1. A bug in the hexagonal lattice refinement is fixed.
2. The Hall symbol interpretation is corrected. Only the Hall symbols from 
SGSY.inc are treated properly now.
3. Some improvements are made in the CIF import-export routines of DDMap.

This is, hopefully, the last pre-GUI version.

Best regards,
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***



  

Re: [ML] Unsettling news from PANalytical

[Leonid Solovyov]

But, hopefully, he (or she) is a designer at least?

--- On Wed, 4/1/09, Smirnova Olga  wrote:

From: Smirnova Olga 
Subject: Re: [ML] Unsettling news from PANalytical
To: martijn.fran...@panalytical.com
Cc: rietveld_l@ill.fr
Date: Wednesday, April 1, 2009, 9:58 AM

The designer of the Universe is not obligatory chemist.  

- Original Message -
>> From: martijn.fran...@panalytical.com
>> To: Leonid Solovyov 
>> Cc: rietveld_l@ill.fr
>> Date: 2009-04-01 15:35:23
>> Subject: Re: [ML] Unsettling news from PANalytical
>> 
>> Dear Leonid, 
>> 
>> are you telling us that you discovered a new element?  ;-) 
>> 
>> 
>> Best regards, 
>>  
>>   
>> Martijn Fransen - Senior Product Manager XRD 
>>  
>> PANalytical 
>> Lelyweg 1 
>> 7602 EA Almelo 
>> The Netherlands 
>> T   +31 546 534345
>> F   +31 546 534 598
>> martijn.fran...@panalytical.com
>> www.PANalytical.com
>> 
>> 
>>  PANalytical
>> The Analytical X-ray Company  
>> 
>> The information contained in this message is confidential and may be 
>> legally privileged. The message is intended solely for the addressee(s). 
>> If you are not the intended recipient, you are hereby notified that any 
>> use, dissemination, or reproduction is strictly prohibited and may be 
>> unlawful. If you are not the intended recipient, please contact the sender 
>> by return e-mail and destroy all copies of the original message.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Leonid Solovyov  
>> 04/01/2009 07:15 AM
>> 
>> To
>> rietveld_l@ill.fr
>> cc
>> 
>> Subject
>> [ML] Unsettling news from PANalytical
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Dear Rietveldians and SDPDists!
>> 
>> According to unsettling news from PANalytical the basic laws of the 
>> universe SUBJECT TO ALTERATIONS WITHOUT NOTICE (probably due to the global 
>> crisis).
>> 
>> See the document: http://l-solovyov.narod.ru/subject_to_alterations.pdf
>> and take care!
>> Leonid
>> 
>> 
>>  Leonid A. Solovyov
>>  Institute of Chemistry and Chemical Technology
>>  660049, K. Marx 42, Krasnoyarsk, Russia
>>  www.icct.ru/eng/content/persons/Sol_LA
>>  www.geocities.com/l_solovyov
>> 
>> 
>> 
>> 



  

Re: [ML] Unsettling news from PANalytical

[Leonid Solovyov]

Not yet, but if PANal helps me... ;-)

--- On Wed, 4/1/09, martijn.fran...@panalytical.com 
 wrote:

From: martijn.fran...@panalytical.com 
Subject: Re: [ML] Unsettling news from PANalytical
To: "Leonid Solovyov" 
Cc: rietveld_l@ill.fr
Date: Wednesday, April 1, 2009, 7:35 AM



Dear Leonid, 



are you telling us that you discovered
a new element?  ;-)    





Best regards, 

  

  

Martijn Fransen - Senior Product Manager XRD 

  


PANalytical 

Lelyweg 1 

7602 EA Almelo 

The Netherlands 
T   +31 546 534345

F   +31 546 534 598

martijn.fran...@panalytical.com

www.PANalytical.com






 PANalytical

The Analytical
X-ray Company  



The information contained in this message is confidential and may be legally
privileged. The message is intended solely for the addressee(s). If you
are not the intended recipient, you are hereby notified that any use, 
dissemination,
or reproduction is strictly prohibited and may be unlawful. If you are
not the intended recipient, please contact the sender by return e-mail
and destroy all copies of the original message.
















Leonid Solovyov 

04/01/2009 07:15 AM




To
rietveld_l@ill.fr


cc




Subject
[ML] Unsettling news from PANalytical


















Dear Rietveldians and SDPDists!



According to unsettling news from PANalytical the basic laws of the universe
SUBJECT TO ALTERATIONS WITHOUT NOTICE (probably due to the global crisis).



See the document: http://l-solovyov.narod.ru/subject_to_alterations.pdf

and take care!

Leonid





 Leonid A. Solovyov

 Institute of Chemistry and Chemical Technology

 660049, K. Marx 42, Krasnoyarsk, Russia

 www.icct.ru/eng/content/persons/Sol_LA

 www.geocities.com/l_solovyov








  

Unsettling news from PANalytical

[Leonid Solovyov]

Dear Rietveldians and SDPDists!

According to unsettling news from PANalytical the basic laws of the universe 
SUBJECT TO ALTERATIONS WITHOUT NOTICE (probably due to the global crisis).

See the document: http://l-solovyov.narod.ru/subject_to_alterations.pdf
and take care!
Leonid


 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov



  

Re: Cagliotti and Other Issues

[Leonid Solovyov]

Dear Simon,

I think it would be nice to have an open web-resource summarizing good practice 
of full-profile refinement, especially if it is supported by real diffraction 
data for, say, simple widely available standards (quartz, silicon, corundum 
etc.) measured at various diffractometers and fitted using different models.
Comparing data and refinement results might help answering such "intimate" 
questions like:
- How good is the program I use (or going to use)?
- What kind of model and parameters are the best for this or that setup and 
sample?
- Is my instrument efficient enough and well aligned?
- Whether the instrument I plan buying or the beamline I think visiting is that 
good as the advertisement suggests?
..
So, the benefits are evident and the "only" problem is to find a coordinator of 
the movement - is it you, Simon? ;-) 

Regards,
Leonid


Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov


--- On Sun, 3/22/09, Simon Billinge  wrote:

> From: Simon Billinge 
> Subject: Cagliotti and Other Issues
> To: "rietveld_l" 
> Date: Sunday, March 22, 2009, 8:50 PM
> Dear Rietvelders
> 
> What is the most complete and authoritative source for
> issues such as
> profile function definitions, what is their scientific
> basis, and when
> are they appropriate to use, etc.?  I am guessing
> there is not
> one-stop-shop solution (Young's book? GSAS manual? Rietveld
> list
> archive?) but advice on this would be helpful.
> 
> I wonder if we should, as a community, put some of this
> stuff on
> wikipedia, or another such place.  In other words,
> distill the
> community's collective knowledge in a single place that can
> be updated
> in the future, and also curated for correctness also by the
> community.
> What are people's thoughts on this?  Rietveldipedia?
> 
> S
>


  

Re: DDM update to 1.6

[Leonid Solovyov]

It seems
that the DDM-page traffic was overloaded at geocities today

At the main
page http://www.icct.ru/eng/content/persons/Sol_LA/ddm.html 
it will be updated tomorrow.


Sorry for the inconvenience!





***

 Leonid A. Solovyov

 Institute of Chemistry and Chemical Technology

 660049, K. Marx 42, Krasnoyarsk,
 Russia

 www.icct.ru/eng/content/persons/Sol_LA

 www.geocities.com/l_solovyov

***




  

DDM update to 1.6

[Leonid Solovyov]

Dear All,

The DDM program is updated to version 1.6 at:

http://www.geocities.com/l_solovyov/ddm.html

The main changes are:

1. Over 100 additional space group settings are added,
   covering all the variants found in the ICSD.

2. The convolution interval assignment procedure is modified.
   It includes now an alternative algorithm based on the correlational
   statistics for data with unknown or unreliable intensity variances.

3. A bug in the hkl selection procedure is fixed that could lead to surplus
   reflections for certain symmetries.

4. The hexagonal symmetry restrictions for the 4-th rank strain broadening
   tensor are corrected.

Best regards and good luck!

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***




  

Re: cRs

[Leonid Solovyov]

Maxim V. Lobanov wrote:

> However, some Rietveld programs do not have good selection of BG functions,
> and it is sometimes problematic to correctly fit the BG - so, I think in this 
> case
> careful BG removal would be the only option.

Not the only option...
You have an option to forget about the background problems at all by using DDM:




www.geocities.com/l_solovyov/ddm.html which does not require the baseline 
modeling or subtraction.

Regards,
Leonid

PS If a supervisor forbids something - forget about it.


Leonid A. 
Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov






  

Re: error in peak positions that is linear in theta

[Leonid Solovyov]

Dear Kurt,

It seems that the problem is in wrong sample-to-detector distance which results 
in the nearly linear angular dependence of the peak displacement.

Regards,
Leonid

*
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
*

--- On Thu, 1/8/09, Kurt Leinenweber  wrote:

> (I hope this list is appropriate for this question).  I am
> trying to set
> up a new D8 diffractometer from Bruker, and have it set up
> with a Vario
> monochromator focusing on a sample in a capillary.  Of
> course I hope to
> do Rietveld refinement on the samples eventually.  But
> there is an error
> in two theta of the peak positions on all samples, and the
> error is
> linear in two theta.  At 40 degrees the error (measured
> minus expected)
> is about 0.020 degrees, at 80 degrees the error is about
> 0.040 degrees,
> etcetera.
> 
>  
> 
> Has anyone ever seen anything like this and do you know
> where it could
> come from?
> 
>  
> 
> Thank you very much,
> 
>  
> 
>
> - Kurt
> 
>  
> 
>  
> 
> *
> 
> Kurt Leinenweber
> 
> Dept. of Chemistry and Biochemistry
> 
> Arizona State University
> 
> Tempe, AZ 85287-1604
> 
>  
> 
> phone (480)-965-8853
> 
> fax (480)-965-2747
> 
>  
> 
> ***


  

RE: calculation of VWDS and SWDS from distributions?

[Leonid Solovyov]

Dear Maxim,

In the expression 
Dv=3mu_4/2mu_3
mu is related to the crystal RADIUS distribution, but in
v=3mu_4/4mu_3
mu is related to the crystal DIAMETER distribution

As for the instrumental and strain contributions, they may be correctly allowed 
for along with the size effect using the TCH pV function from which you may get 
estimations for VWDS and AWDS.
See, for instance, EXAMPLE3 in the DDM suite where the refinement of the Ceria 
sample from the Size-Strain Round Robin is presented.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***

--- On Mon, 12/15/08, Максим В. Лобанов  wrote:

> From: Максим В. Лобанов 
> Subject: RE: calculation of VWDS and SWDS from distributions?
> To: "rietveld_l@ill.fr" 
> Cc: "Eduard E. Levin" 
> Date: Monday, December 15, 2008, 6:04 AM
> Dear colleagues,
> 
> First of all, thanks to Dr. Ortiz for the
> advice/explanation. 
> 
> I would like to point out some discrepancy in the standard
> formulae for VWDS/SWDS, which are given in various
> well-respected articles.
> 
> 1) N.C. Popa, D. Balzar, JAC 35, 338, formulae 7-8:
> Dv=3mu_4/2mu_3 (7)
> and
> Da=4mu_3/3mu_2 (8)
> 
> 2) P. Scardi, M. Leoni, JAC 39, 24, formulae 1a-1b:
> s=2mu_3/3mu_2 (1a)
> and
> v=3mu_4/4mu_3 (1b)
> 
> It seems that these definitions are differing merely by a
> factor of two.
> I am curious if anybody could clarify this point.
> 
> Sincerely,
> Maxim.
> 



  

Re: calculation of VWDS and SWDS from distributions?

[Leonid Solovyov]

Dear Maxim,

The formulae 
 Dv=3mu_4/2mu_3
 Da=4mu_3/3mu_2
are valid for spherical crystallites only.
Accordingly, in the expression
 mu_i=Int[0, Infinity]{x^i*p(x)dx}
x should be the radius of spherical crystallite, but not “particle size”.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***

--- On Mon, 12/8/08, Максим В. Лобанов <[EMAIL PROTECTED]> wrote:

> From: Максим В. Лобанов <[EMAIL PROTECTED]>
> Subject: calculation of VWDS and SWDS from distributions?
> To: "rietveld_l@ill.fr" 
> Date: Monday, December 8, 2008, 2:04 PM
> Dear colleagues,
> 
> I am facing a problem of correlating laser scattering (DLS)
> and X-ray diffraction data.
> For correct comparison, I need either to calculate some
> model distribution from X-ray data (this is feasible
> assuming lognormal distribution - there are ready software
> solutions for that) or typical "X-ray sizes" (Dv
> and/or Da) from given distributions.
> The inverse task (calculating Dv and/or Da from given
> distributions) appears to be very simple, but it seems there
> is no ready software solution, and I need to manually
> integrate the data. But before doing  that I would like just
> to be sure that I use correct formulae.
> I read the paper dealing with that in great detail (JAC,
> 35, 338 by Popa & Balzar, Ref. 1), but it is too
> mathematical, and I am not completely confident if I
> understood everything correctly.
>  
> If we denote distribution (normalized to unity) as p(x),
> x=particle size
> then, according to Ref.1:
> Dv=3mu_4/2mu_3 (1)
> and 
> Da=4mu_3/3mu_2 (2)
> 
> Do I understand correctly, that moments mu_i are just:
> 
> mu_i=Int[0, Infinity]{x^i*p(x)dx}
> 
> Or there are some missing factors somewhere?
> 
> Sincerely,
> Maxim.
>  
> ---
> Dr. Maxim Lobanov
> R&D Director
> Huntsman-NMG
> mailto: [EMAIL PROTECTED]
> 
> *
> If you encounter any difficulties 
> sending e-mails to the addresses in huntsman-nmg.com
> domain,
> this could be due to the our spam filter malfunction.
> In case of such an event please send a message to
> [EMAIL PROTECTED]
> 
> Please note that the old domain nmg.com.ru does not exist
> anymore - 
> please update your address book accordingly


  

Re: Can anybody do me a favor to refine my Y2O3?

[Leonid Solovyov]

Dear  Li,

I don't use GSAS, but I refined your data using the DDM program that gave 
nearly perfect fit. The DDM parameters file is attached and the program is 
freely available from 
http://www.icct.ru/eng/content/persons/Sol_LA/ddm.html
or
http://www.geocities.com/l_solovyov/ddm.html

I must note, however, that the diffraction peaks in your pattern are very broad 
which may indicate a misalignment of your instrument or some problems with the 
X-ray tube. For this setup of X'Pert MPD the width of peaks below 60 degrees 
2theta should be less that 0.1, but your width is around 0.3 - too big!

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***

--- On Fri, 12/5/08, Mingtao Li <[EMAIL PROTECTED]> wrote:

> From: Mingtao Li <[EMAIL PROTECTED]>
> Subject: Can anybody do me a favor to refine my Y2O3?
> To: "Rietveld_l" 
> Date: Friday, December 5, 2008, 2:07 PM
> To all,
> I am learning rietveld refinement. First I want to
> get my
> instrumental parameter file. So I collected xrd pattern of
> cubic Y2O3
> on a X'pert pro MPD diffractiometer. The experimental
> conditions were
> listed as following:
> 
> Cu KAlpha:
>KAlpha1:1.5405980
>KAlpha2:1.5444260
> ratio KAlpha2/KAlpha1:0.5000
> 
> Incidental Beam Path:
>soller slit:0.02rad
>divergence slit 1 degree
>anti-scatter slit 2 degree
>incidental mask 10 mm
> 
> Goniometer Radius 240mm
> 
> Diffracted Beam Path
> antiScatterSlit: AS Slit 6.6mm
> sollerSlit:0.02rad
> filter:nickel (thickness:0.02mm)
> Detector:X'Celerator
> 
> The xrdml attached is the original pattern file. The cif
> file of cubic
> Y2O3 and gsa file of the pattern are also attached.
> 
> I have tried to do the refinement using GSAS many times
> following the
> instructions from http://www.cins.ca/cpdw/notes.html., but
> the results
> were quite different every time, especially the unit cell.
> Now I am
> very confused. Why did that happen? Shouldn't I refine
> S/L and H/L? So
> here I am for help. Can anyone do me a favor to refine my
> Y2O3 give a
> "standard" result?
> 
> Thanks in advance.
> 
> -- 
> **
> Mingtao Li, Ph.D. Candidate
> State Key Laboratory of Multiphase Flow in Power
> Engineering
> School of Energy and Power Engineering, Xi'an Jiaotong
> University
> No.28, Xianning West Road, Xi'an, Shaanxi, 710049, P.R.
> China
> Tel: +86-29-82668296-11  Fax:
> +86-29-82669033
> E-mail: mingtao dot li at gmail dot com
> **


  

Y2O3.ddm
Description: Binary data

RE: Rietveld: U,V,W

[Leonid Solovyov]

Brian wrote:
>U and W should be instrumental constants that will not change with >sample, 
>while V can have both an instrumental and a
>residual stress component.

Maxim wrote:
>as far as I understand, the strain broadening term should have FWMM~theta 
>>dependence, i.e. Lorentzian Y in "standard" (GSAS) notation.
>For the Gaussian part you have
>FWHM^2=U*tan^2(th)+V*tan(th)+W+P/cos^2(th)
>and the term that varies roughly as ~theta is U, not V.
>Therefore, based on that and probably erroneously, I used to refine U 
>>parameter rather than V (+ P, X, Y, of course).
>I am wondering if somebody could make this more clear?

Dear Brian and Maxim,

In fact, the term responsible for the Gaussian strain component is U, not V.

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***


  

Re: I am a newcome, how can I begin my rietveld refinement analysis

[Leonid Solovyov]

At the
initial stage you don’t need precise values of U, V, and W. You may set U=0,
V=0, and W equal to the squared FWHM of the highest peak.

 



Leonid


*
 
Leonid A. Solovyov
 
Institute of Chemistry and Chemical Technology
 
660049, K. Marx 42, Krasnoyarsk, Russia
 
www.icct.ru/eng/content/persons/Sol_LA

  www.geocities.com/l_solovyov

*
--- On Sun, 11/30/08, Mingtao Li <[EMAIL PROTECTED]> wrote:

Hi, everyone,
 I am a newcome to Rietveld refinement. Actually I am a student
majored in photocatalytic splitting water for hydrogen production. We
want to analysis the structures of our photocatalysts via rietveld
method. For that purpose we got a X'pert Pro diffractionmeter from
Panalytica about 3 years ago. But rietveld is too difficult to start.
Now I have read some books and downloaded some programs from ccp14
such as fullprof, checkcell and so on. Also I have tested some
examples. However I am still confused. How can I determine the initial
value of some parameters such as U, V and W. Maybe I need a
Instrumental Resolution Function file, but how can set that file?

Can anybody give me some advice about this?

thanks a million.

-- 
Mingtao Li
State Key Laboratory of Multiphase Flow in Power Engineering
School of Energy and Power Engineering
Xi'an Jiaotong University
Xi'an, 710049
P.R.China
Tel: +86-29-8266 8296
Fax: +86-29-8266 9033
Email: [EMAIL PROTECTED]



  

DDM update

[Leonid Solovyov]

Dear All,

The DDM program is updated at
www.icct.ru/eng/content/persons/Sol_LA/ddm.html
and mirrored at
www.geocities.com/l_solovyov/ddm.html

The main changes:
1. DDMap utility is added. This program reads crystal data and structure 
factors from CIF file, calculates Fourier and Patterson maps including the 
Symmetry and Image minimum functions and allows viewing manually chosen 
sections of the 3D density map.   The structure model may be built/modified 
within DDMap by adding/removing atoms.
2. The space group interpretation and reflection generation routines were 
changed to more flexible and reliable ones. The rhombohedral setting and the 
acentric origin choice 1 are allowed.
3. The symmetry restrictions on all parameters are imposed automatically by the 
program.
4. An automatic procedure for the initial overall scale factor estimation is 
added.
2. New weighting scheme is added that is chosen now by IWGHT flag.
3. New asymmetry parameter P2 responsible for the lattice-gradient effect is 
added.

Other changes are listed in history.txt

Best regards,
Leonid Solovyov

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 www.geocities.com/l_solovyov
***



  

RE: question on size-strain analysis - question for Fullprof users

[Leonid Solovyov]

Dear Maxim,

Actually, there are no standard notations for these parameters of TCH pV. In 
different programs they are designated differently.

Regards,
Leonid

--- On Thu, 11/13/08, Maxim V. Lobanov <[EMAIL PROTECTED]> wrote:

> From: Maxim V. Lobanov <[EMAIL PROTECTED]>
> Subject: RE: question on size-strain analysis - question for Fullprof users
> To: rietveld_l@ill.fr
> Date: Thursday, November 13, 2008, 1:00 PM
> Dear Leonid, 
> thank you very much. Indeed it is not "really
> simple": averaging procedure is not straightforward...
> 
> Now a question to Fullprof users:
> it seems that Fullprof is using non-standard designation
> for TCH PV parameters.
> I mean by standard the one which is adopted e.g. in
> D.Balzar et al., JAC 37, 911 (2004) - formula 8b,
> i.e.
> Gamma_L = x/cos(theta) + X/cos(theta) + Y*tan(theta), i.e.
> Lorentzian size broadening is given by X value. GSAS is also
> using this notation.
> 
> In the Fullprof manual it is stated that the designation is
> opposite:
> Gamma_L = X*tan(theta) + Y/cos(theta)
> 
> I am curious if this is still the case, or maybe by chance
> it was corrected in some recent Fullprof update?
> 
> Sincerely,
> Maxim.
> 



  

RE: question on size-strain analysis

[Leonid Solovyov]

Dear Maxim,

Yes, these calculations can be done for TCH pV relatively simply (not “really 
simply” :-).
The crystal size estimations from the refined parameters of TCH pV are 
included, for instance, into the DDM program 
[www.icct.ru/eng/content/persons/Sol_LA/ddm.html] and the formulae are 
described in Page 12 of the DDMguide.
Note, however, that these estimations are valid only for simple crystal size 
distributions.

Best regards,
Leonid



--- On Thu, 11/13/08, Maxim V. Lobanov <[EMAIL PROTECTED]> wrote:

> From: Maxim V. Lobanov <[EMAIL PROTECTED]>
> Subject: RE: question on size-strain analysis
> To: rietveld_l@ill.fr
> Date: Thursday, November 13, 2008, 6:47 AM
> Dear colleagues,
> 
> I would like first to thank everybody who responded to my
> question on
> Gaussian size broadening. 
> 
> And now would like to ask another closely related (but
> "more practical")
> question:
> I think the easiest way to do particle size estimate in
> case when one has
> mixed alpha1/alpha2 (and/or a series of similar samples) is
> to do Rietveld
> or Le Bail fit and estimate particle size from the refined
> profile
> parameters (e.g. P and X in TCH PV).
> But once you have refined values for both P and X, you
> easily calculate
> "Lorentzian size" and "Gaussian size" -
> but (citing Woodward's lecture on
> size-strain analysis), 
> "it is not immediately clear to me how to combine
> these results and get an
> accurate estimate of the crystallite size (though perhaps
> there may be a
> good way to do this)"
> Can anybody suggest such "good way"? This must be
> something really simple...
> 
> Sincerely,
> Maxim.
> 



  

Re: Anisotropic peak broadening with TOPAS

[Leonid Solovyov]

Dear Frank,

I don’t have an exact recipe for Topas, but a general consideration of the 
problem you face with may be found in J. Appl. Cryst. (2008) 615–627. If you 
read the paper don’t miss the last sentence of the Conclusions :)

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Wed, 10/29/08, Frank Girgsdies <[EMAIL PROTECTED]> wrote:

> From: Frank Girgsdies <[EMAIL PROTECTED]>
> Subject: Anisotropic peak broadening with TOPAS
> To: Rietveld_l@ill.fr
> Date: Wednesday, October 29, 2008, 11:04 AM
> Dear Topas experts,
> 
> this is my first email to the list, so if you would like
> to know something about my background, please refer to
> the "about me" section at the end of this mail.
> 
> My question is concerning advanced modeling of anisotropic
> peak broadening with Alan Coelhos program
> "Topas".
> 
> I'm working on a transition metal mixed oxide phase of
> orthorhombic symmetry. Composition, lattice parameters,
> crystallite size etc. may vary from sample to sample.
> I'm using Topas to fit the powder patterns with a
> "structure phase". If the peaks exhibit more or
> less
> homogeneous peak widths, I refine the "Cry Size
> L"
> and/or "Cry Size G" parameters to model the peak
> shapes. Thus, I can obtain the LVol-IB as a measure
> for the average crystallite size.
> 
> In some cases, however, I observe strongly anisotropic
> peak broadening, with the 00l series of reflections
> being much sharper then the hk0 and hkl reflections.
> This observation fits nicely with the electron
> microscopy results, where the crystals are needles of
> high aspect ratio, the long axis being the c-axis of
> the crystal (thus, I assume that the peak broadening
> is dominated by the crystallite size effect, so
> let us ignore the possibility of strain etc.).
> In such case, I leave the GUI and switch to launch mode,
> where I can successfully model the anisotropic peak
> broadening with a second order spherical harmonics
> function, following section 7.6.2. of the Topas (v3.0)
> Technical Reference. So far, so good.
> 
> However, since the peak width is now primarily a
> function of hkl (i.e. the crystallographic direction)
> instead of a function of 1/cos(theta), I lose the size
> related information. Of course, I'm aware of the
> fact that the LVol-IB parameter is based on the
> 1/cos(theta) dependence and thus cannot be calculated
> for a spherical harmonics model.
> But the peaks still have a width, so it should be
> possible somehow to calculate hkl-dependent size
> parameters. And this is the point where I'm hoping
> for some input from more experienced Topas users.
> 
> I could imagine three directions of approach:
> 
> A) The refined spherical harmonics functions
> yields a set of coefficients. I'm not a mathematician,
> so how to make use of these coefficients for my
> purpose is beyond my comprehension.
> I imagine the refined spherical harmonics function
> as a 3-dimensional correction or scaling function,
> which yields different values (scaling factors)
> for different crystallographic directions.
> Thus, it should be possible to calculate the
> values for certain directions, e.g. 001 and 100.
> I would expect that the ratio of these two values
> is somehow correlated with the physically observed
> aspect ratio of the crystal needles, or at least a
> measure to quantify the "degree of anisotropy".
> Is there a recipe to re-calculate (or output) these
> values for certain hkl values from the set of
> sh coefficients?
> 
> B) As far as I understand the spherical harmonics
> approach as given in the Topas manual, it REPLACES
> the Cry Size approach. However, it might be possible
> to COMBINE both functionalities instead. Within a
> given series of reflections (e.g. 00l) the
> 1/cos(theta) dependence might still be valid.
> I could imagine that the spherical harmonics model
> might be used as a secondary correction function
> on top of a 1/cos(theta) model.
> I think such approach would be analogous to the use
> of spherical harmonics in a PO model, where the
> reflection intensities are first calculated from
> the crystal structure model and then re-scaled
> with a spherical harmonics function to account for
> PO.
> If such an approach would be feasible, it should
> be possible to extract not only relative (e.g. aspect
> ratio) information as in A), but direction dependent
> analogues of LVol-IB, e.g. LVol-IB(a), LVol-IB(b)
> and LVol-IB(c) for an orthorhombic case.
> 
> C) One could leave the spherical harmonics approach
> and go to a user defined model, which refines different
> Cry Size parameters for different crystal directions.
> In my case, two parameters would probably be sufficient,
> one for the c-direction, and a common 

Re: Quantitative analysis

[Leonid Solovyov]

Dear Mario,

One more possible problem of applying preferred orientation corrections in QPA 
is that not all of them are normalized. For example, the March-Dollase 
correction is normalized and can be applied safely, but the Rietveld-Toraya 
correction is inapplicable to QPA as it does not preserve the scale 
normalization. 

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Mon, 10/27/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:

> From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Subject: Quantitative analysis
> To: Rietveld_l@ill.fr
> Date: Monday, October 27, 2008, 3:48 PM
> Dear all,
> 
> I have this question,
> 
> I have been refined one mixture (of well-know percentage
> composition) of
> CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation
> in CaCO3 (104)
> and CaF2 (111) with good results. When I add to the mixture
> FeCO3 and I
> refine with preferential orientation (104), it happens that
> when I don´t
> apply the preferential orientation in all this phases, I
> have correct
> values of percentage composition, but when I apply the
> preferential
> orientation the refinement is good but with incorrect
> values of percentage
> composition. This experiment has been taken in Bragg
> Brentano geometry.
> How I should refine this mixture?
> 
> Thanks a lot by your help.
> 
> Mario Macías
> Universidad Industrial de Santander
> Colombia


  

Re: GSAS: Microstrain parameters in rhombohedral SGs

[Leonid Solovyov]

Dear Franz,

The symmetry-specific expressions for the Shkl tensor are given in 
GSASManual.pdf pages 150-151.

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***


--- On Sun, 10/26/08, Franz Werner <[EMAIL PROTECTED]> wrote:

> From: Franz Werner <[EMAIL PROTECTED]>
> Subject: GSAS: Microstrain parameters in rhombohedral SGs
> To: rietveld_l@ill.fr
> Date: Sunday, October 26, 2008, 7:38 AM
> Hello All
> 
> Can anyone tell me how the indices of the S(hkl) parameters
> are treated in GSAS in the case of a rhombohedral SG in
> hexagonal setting? Do the hkl refer to the rhombohedral or
> hexagonal axes? I'm currently refining in SG R -3 (no.
> 148) in hexagonal setting. Furthermore I'd like to know
> the expression of Gamma_S^2 (function of S400, S004, S202
> and S310) for this SG as I can't find it in the GSAS
> manual.
> 
> Thanks for your help.
> 
> Regards
> Franz Werner
> -- 
> Pt! Schon vom neuen GMX MultiMessenger gehört? Der
> kann`s mit allen: http://www.gmx.net/de/go/multimessenger


  

Re: question on size-strain analysis

[Leonid Solovyov]

Hi Nicolae,

Nice to hear from you!
I couldn't help noting that in reality your emergence in the Rietveld list is 
similarly rare as the narrow size distribution :-). Instrumental problems are 
far more regular.

Best wishes,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:   +7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Tue, 10/21/08, Nicolae Popa <[EMAIL PROTECTED]> wrote:

> From: Nicolae Popa <[EMAIL PROTECTED]>
> Subject: Re: question on size-strain analysis
> To: [EMAIL PROTECTED], rietveld_l@ill.fr
> Date: Tuesday, October 21, 2008, 11:39 AM
> Hi,
> 
> Besides strain and instrument also size broadening can be
> close to a 
> Gaussian if the crystallite size distribution is very
> narrow. For zero 
> dispersion of size distribution the size peak profile is
> about 75% Gaussian 
> and 25% Lorentzian (on tails). For details see JAC (2002)
> 35, 338-346 (self 
> citation) and other ref. cited there (Langford, Louer,
> Scardi (2000))
> 
> Best,
> 
> Nicolae Popa
> 



  

Re: question on size-strain analysis

[Leonid Solovyov]

Dear Maxim,

Gaussian peak shape is, normally, related to the instrumental, strain and/or 
lattice distribution broadening. The Williamson-Hall plot shows the dependency 
of broadening on the diffraction angle and if this dependency can not be 
explained by strain then it is most probably instrumental. If you use the 
Bragg-Brentano geometry a possible reason might be a loose powder, sample 
misalignment or surface roughness.

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology  K. Marx av., 42
660049, Krasnoyarsk  Russia
Phone: +7 3912 495663
Fax:+7 3912 238658
www.icct.ru/eng/content/persons/Sol_LA
***

--- On Tue, 10/21/08, Maxim V. Lobanov <[EMAIL PROTECTED]> wrote:

> From: Maxim V. Lobanov <[EMAIL PROTECTED]>
> Subject: question on size-strain analysis
> To: rietveld_l@ill.fr
> Cc: "Дмитрий А. Павлов" <[EMAIL PROTECTED]>
> Date: Tuesday, October 21, 2008, 7:20 AM
> Dear colleagues,
> 
> I have a probably very basic question related to
> size-strain analysis:
> 
> we have a pattern of a nanocrystalline oxide, which shows
> (from
> Williamson-Hall plot) almost purely size broadening, and
> shape of
> reflections is to good accuracy Gaussian.
> I am curious what type of microstructure this Gaussian
> behavior can reflect.
> Maybe it is just something usual, but so far I had only
> observed
> predominantly Lorentzian broadening in similar materials...
> 
> Sincerely,
> Maxim.
> 
> 
> ---
> Dr. Maxim Lobanov
> R&D Director
> Huntsman-NMG
> mailto: [EMAIL PROTECTED]
> 
> *
> If you encounter any difficulties 
> sending e-mails to the addresses in huntsman-nmg.com
> domain,
> this could be due to the our spam filter malfunction.
> In case of such an event please send a message to
> [EMAIL PROTECTED]
> 
> Please note that the old domain nmg.com.ru does not exist
> anymore - 
> please update your address book accordingly


  

Re: Question on QPA - Amorphous/crystalline mix

[Leonid Solovyov]

Dear Lee,

Your calculations are correct provided the allowances for microabsorption and 
other effects were made properly.

Regards,
Leonid

--- On Tue, 10/14/08, Lee Gerrard <[EMAIL PROTECTED]> wrote:

> From: Lee Gerrard <[EMAIL PROTECTED]>
> Subject: Question on QPA - Amorphous/crystalline mix
> To: rietveld_l@ill.fr
> Date: Tuesday, October 14, 2008, 1:20 PM
> I have a question for the list as I know there are a number
> of people
> working on QPA. Ok the question is as follows:-
>
> We have a mixture of a number of crystalline phases (A and
> B) and an
> amorphous (glassy) phase. We can do Rietveld refinement on
> this and get
> weight percentage (wt.%) values for the crystalline
> components. We have
> added a known amount of corundum as a standard and refined
> again.
> Example values we get are as follows:-
>
> Phase A  10 wt.%
> Phase B  50 wt.%
> Corundum 40 wt.%
>
> BUT we know we have added only 33 wt.% corundum - are we
> able to
> calculate the wt.% of the amorphous content from the known
> values? I
> have tried scaling/ratio'ing the values to the known
> corundum amount
> therefore giving:-
>
> Phase A  8.25 %
> Phase B  41.25 %
> Corundum 33 %
>
> TOTAL82.5 %
>
> which leaves 17.5 % left over. Hence must be the amorphous
> part??
>
> I am not totally convinced by this method at all and would
> love to know
> how is best to go about solving this problem.
>
> Many thanks,
>
> Lee
> ~~~
> Dr. Lee A. Gerrard BSc CChem CSci MRSC
> Materials Scientist
> 
> Materials Science Research Division
> SB40.1
> AWE Plc
> Aldermaston, Reading,
> Berkshire
> RG7 4PR
> 
> Tel:  +44 (0)118 982 6516
> Fax: +44 (0)118 982 4739
> Email: [EMAIL PROTECTED]
> ~~~


  

Re: Beta iso

[Leonid Solovyov]

Dear Mario,

Negative isotropic displacement parameters are physically meaningless and are 
indicative of problems in either the model or the data (or both). 
Possible reasons: 
low sensitivity of refinement to displacement parameters due to insufficient 
data quality;
incorrect refinement of peak shape and/or FWHM parameters;
improperly corrected or neglected 2teta-dependent alterations of diffraction 
intensities due to instrument/sample misalignment, polarization, absorption, 
surface roughness etc.;
unaccounted partial occupation of atomic positions by heavier atoms.
The list of possible reasons is incomplete, of course……

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx 42
660049, Krasnoyarsk
Russia
Email: [EMAIL PROTECTED]
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***

--- On Tue, 9/23/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:

> From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Subject: Beta iso
> To: Rietveld_l@ill.fr
> Date: Tuesday, September 23, 2008, 3:34 PM
> Dear all rietvelders,
> 
> Can I obtain negative value of Beta isotropic?
> 
> I have obtained good value of refinements with negative
> value of Beta
> isotropic. Is that possible? I mean, the Beta isotropic
> depend of
> quadratic displacement of the atom.
> 
> Thanks a lot for your help,
> 
> Mario Macías
> UIS, Colombia


  

Re: Beginer problems, difficulty charecterizing our diffractometer...

[Leonid Solovyov]

Dear Blaise,

The strong peak asymmetry may result from high-divergence Soller slits 
installed in your instrument. You may consider using sollers of lower 
divergence that normally allows easier peak shape approximation and, besides, 
increases the resolution (at the expense of intensity, of course).
You also mentioned ‘aluminum sneaking into the beam’ which means that you don’t 
use the sample spinner. This may create additional problems related to poor 
particle statistics especially if the quarts powder is not fine enough.
Many related problems are well discussed in ‘Rietveld refinement guidelines’ J. 
Appl. Cryst. (1999) 36.

Best regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
K. Marx 42
660049, Krasnoyarsk
Russia
Email: [EMAIL PROTECTED]
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***


--- On Wed, 9/17/08, Mibeck, Blaise <[EMAIL PROTECTED]> wrote:

> From: Mibeck, Blaise <[EMAIL PROTECTED]>
> Subject: Beginer problems, difficulty charecterizing our diffractometer...
> To: rietveld_l@ill.fr
> Date: Wednesday, September 17, 2008, 8:22 PM
> I am re-learning GSAS to bring Rietveld to my department
> (for the first
> time). We have an old Phillips Xpert. 
> 
>  
> 
> I am trying to refine a quartz standard to acquire my
> profile and instrument
> parameters for this instrument and have yet to get my Chi^2
> below 500. The
> instrument is not in my direct control. I have caught and
> asked them to
> correct a few problems already (dwell time too low,
> aluminum sneaking into
> the beam, etc...) and this has helped. I would like not to
> annoy them any
> more than I have too. 
> 
>  
> 
> At this point I think my high Chi^2s are mainly due to low
> angle asymmetric
> peaks that my fit is not able to copy - the asym is not
> terrible but may be
> messing me up. I am getting better results with peak
> profile functions 3 and
> 4, but unable to get Chi^2 below 500. My scans go up to 70
> degrees 2theta.
> 
>  
> 
> I would like to tell the people caring for the instrument
> that my problem is
> on their end, but I am not confident in my own refining
> skills to say this.
> When I work with the tutorials or standard data from my
> graduate school
> experiment I am ok - I think I am proceeding in a
> reasonable way, although I
> can get stuck here and there. 
> 
>  
> 
> I would like to find out if I am doing something
> incorrectly or if the
> problem is instrument related. I hate to bug one of you but
> wonder if I
> could get someone to look at my work?? Is there a better
> forum for asking
> for this kind of help? 
> 
>  
> 
> Kindest regards to all of you,
> 
> Blaise
> 
>  
> 
>  
> 
>  
> 
>  
> 
>  
> 
>  
> 
> * * * * * * * * * * * * * 
> 
> Blaise Mibeck 
> 
> Research Scientist
> 
> Energy & Environmental Research Center
> 
> University of North Dakota
> 
> 15 North 23rd Street, Stop 9018
> 
> Grand Forks, ND 58202-9018
> 
>  
> 
> Phone: (701) 777-5077
> 
> Email: [EMAIL PROTECTED]
> 


  

RE: advice on new powder diffractometer

[Leonid Solovyov]

> It seems to me that if there is no internationally accepted
definition
> of signal to noise ratio in powder diffraction, then let me suggest
> that
> this forum might be a way to define it once and for all. How about
> this?
>   SNR = (P-B)/SQRT(B). 
>
> Of course this would only give a  value for a single peak. I suppose
> one could also define a global SNR as a sum over all 
> Global SNR = sum over peaks (P-B)/SQRT(B).
>
> Does this make sense?
> Mike

A more overall value would be a normalized sum of the ratios
(Ip-Ib)/sqrt(Ib), where Ip and Ib are the profile intensities of the
pattern and the background for each datapoint.

Leonid



  

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RE: advice on new powder diffractometer

[Leonid Solovyov]

Dear Mike,

Normally, changing sollers must not influence the signal/background
ratio. Wider sollers, however, make the primary beam wider and if the
sample diameter is small then a parasitic scattering from the sample
holder edges may appear.

I am really surprised that moving from 0.04 Soller slits to 0.02 you
got 25 times intensity reduction. When I change the primary soller from
0.04 to 0.02 the intensity drops ~2 times, so if you changed both the
primary and the secondary sollers the intensity should decrease ~4
times, but not 25 times.

Leonid Solovyov

> How do you define signal to noise in powder diffraction? I have seen
>  this term used several times, but I have not found a definition so
far
>  with regard to powder diffraction per se. 
> I have just done two runs on a Panalytical one with 0.04 soller slits
>  and one with 0.02 (both with a CuKa1 premonochromator) both for
about 9
>  hours. The strongest peak for the 0.02 case is 2700 counts, half
width
>  0.08 degrees and a background of 25 counts. The same peak with the
0.04
>  slits  has 7 counts, half width 0.11 degrees and a background of
>  700 counts.
>
>
> Mike Glazer



  

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Re: advice on new powder diffractometer

[Leonid Solovyov]

> Yes it is mainly down to the Soller slits, 
> there was a very large thread on
> soller slits somewhere in the Rietveld archives
> about this discussion. I think the down side of
> changing the soller slits is a move away from the
> optimum FWHM that can be obtained?

Changing sollers from 0.04 rad to 0.02 or 0.01 reduces the asymmetry,
the FWHM and the intensity, so the peak shape and the resolution become
more optimal but the intensity is sacrificed.



  

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