RE: RIET: Source code for the Uni-tuebingen MEED Maximum Entropy software
The Internet Archive has it: http://web.archive.org/web/20051108111330/http://www.uni-tuebingen.de/uni/pki/maxent/maxent.html The downloads work (or at least, they did for me...) Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au -Original Message- From: Lachlan Cranswick [mailto:lachl...@magma.ca] Sent: Monday, 10 August 2009 04:59 To: rietveld_l@ill.fr Subject: RIET: Source code for the Uni-tuebingen MEED Maximum Entropy software Hi, Does anyone have a copy or know where the Uni-tuebingen MEED Maximum Entropy software can be obtained from? It used to be at http://www.uni-tuebingen.de/uni/pki/maxent/maxent.html Thanks, Lachlan --- Lachlan M. D. Cranswick Contact outside working hours / Coordonnees en dehors des heures de travail: NEW E-mail / courriel: lachlanc *at* magma.ca Home Tel: (613) 584-4226 ; Cell/mobile: (613) 401-6254 WWW: http://lachlan.bluehaze.com.au/ P.O. Box 2057, Deep River, Ontario, Canada, K0J 1P0 (please use clear titles in any Email - otherwise messages might accidentally get put in the SPAM list due to large amount of junk Email being received. If you don't get an expected reply to any messages, please try again.) (Essayez d'utiliser des titres explicites - sans quoi vos messages pourraient aboutir dans un dossier de rebuts, du fait de la quantite tres importante de pourriels recue. Si vous n'obtenez pas la reponse attendue, merci de bien vouloir renvoyer un message.)
RE: Cagliotti and Other Issues
-Original Message- From: May, Frank [mailto:frank.l@umsl.edu] My recollection is the Cagliotti function was adapted to the x-ray case when we had low resolution x-ray instruments and slow (or no) computers. Now that we have high resolution instruments and fast computers, why does this inappropriate function continue to be used? There's probably a great deal of it's always been done this way in why its used, in addtion to a lack of education in when it should be used, as well as Let's tick this box and see what happens... :( On another note, the world is venturing into the infinitely small realm of nano-particles As the relative fraction of the bulk becomes smaller, both the physical structure as well as the mathematics used to describe the bulk suffer from termination-of-series effect, do they not? Does any of this make sense? Any thoughts? This is talked about by Grey and Wilson*. They show that while you can refine diffraction data from nanosize titania particles, the numbers (cell params in this case...) that you get out might not represent what is actually there. Basically, the assumption that there is an infinite lattice breaks down. *Titanium vacancy defects in sol-gel prepared anatase Grey, I; Wilson, N JOURNAL OF SOLID STATE CHEMISTRY (0022-4596); Volume: 180; Issue: 2; Date: 2007; pg. 670-678 Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au
RE: UVW - how to avoid negative widths?
From what I've read of Cagliotti's paper, the V term should always be negative; or am I reading it wrong? Additionally, there is some good work on the use of the Cagliotti (and TCHZ) functions in the paper by Young and Desai; it also goes over how to incorporate sample dependent terms into the expression. Young, R. A. Desai, P. 1989, 'Crystallite Size and Microstrain Indicators in Rietveld Refinement', Archiwum Nauki o Materialach, vol. 10, no. 1-2, pp. 71-90. Alan Hewat wrote: if you have access to the refinement code. This is why I love Topas. All of the the code used in the refinements is there for you to see! :) Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au
RE: GSAS data formats
Bob I agree that ESD or FXY[E] appear to be the best units to use, but you can't always dictate which format you receive your data in... So with the STD format, the total number of counts for a point is given by counter*intensity and the esd is given by sqrt(intensity/counter)? Also, going on with your comment about the FXYE format, is TOFT still centidegrees*32 (as per the manual) or just plain centidegrees? Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au From: Brian H. Toby [mailto:brian.t...@anl.gov] Sent: Tuesday, 17 March 2009 00:31 To: vondre...@anl.gov Subject: Re: GSAS data formats I don't think this went to the mailing list On Mar 16, 2009, at 7:44 AM, Robert Von Dreele wrote: Hi, Brian is correct in that the 'FXYE' format is best as it is the simplest to implement. It requires 3 columns of data in free format (either floating point or exponental forms are OK). 1st column is position (in centidegrees), 2nd is intensity (corrections can be applied if needed) 3rd is esd (error propagation for corrections applied here). The STD format is no. counters intensity. The intensities are all on same basis i.e. the average over the number of counters used to collect that point. GSAS calculates the esd ( weight) using the number of detectors. BTW - the GSAS Manual indicated that records need be 82 characters long. This is no longer true. Records can be shorter. Best, Bob Von Dreele - Original Message - From: Brian H. Toby brian.t...@anl.gov Date: Monday, March 16, 2009 0:30 am Subject: Re: GSAS data formats To: matthew.row...@csiro.au Cc: rietveld_l@ill.fr I do not recommend using this format. Better choices are the ESD variant on this, where numbers are alternated intensity, esd, intensity... (and there are a lot more digits for each number) or the FXYE format, which has angle, intensity, and optionally esd, one entry per line in free format. My recollection on this is that YO is the total number of counts, so the normalized Intensity = YO/n and the error on that is SQRT(YO)/n. The idea being that not all measurements are made with the same number of detectors. Brian On Mar 16, 2009, at 12:02 AM, matthew.row...@csiro.au wrote: Hi all I'm going over the GSAS data format (by reading the manual), trying to figure out how it works, and I've come up with a couple of questions: 1) In a STD data set, the manual says that NCTR is the number of counters and YO is the n number of counts per counter. So, for a single data point 3 3452, is the total counts =3*3452? What is the error? Sqrt(3*3452), 3*sqrt(3452) or sqrt(3452/3)? 2) What is the data format for type = ALT? The manual (http:// www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/gsas/public/gsas/manual/ GSASManual.pdf) doesn't say... Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au Brian H. Toby, Ph.D.office: 630-252-5488 Senior Physicist/Materials Characterization Group Leader Advanced Photon Source 9700 S. Cass Ave, Bldg. 433/D003 work cell: 630-327-8426 Argonne National Laboratory secretary (Marija): 630-252-5453 Argonne, IL 60439-4856 e-mail: brian dot toby at anl dot gov We will restore science to its rightful place, and wield technology's wonders... We will harness the sun and the winds and the soil to fuel our cars and run our factories... All this we can do. All this we will do. Brian
RE: cRs
It's German... verboten == forbidden. You should never delete the background from a diffraction pattern prior to (Rietveld) analysis. It changes peak positions and shapes and generally is bad. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au -Original Message- From: Olga Smirnova [mailto:olga.smirn...@hw7.ecs.kyoto-u.ac.jp] Sent: Wednesday, 4 March 2009 16:30 To: Brian O'Connor Cc: rietveld_l@ill.fr Subject: Re: cRs According to my computer, I received your response 4 minutes earlier than forwarded the email. What is 'verbotten' (volabulary does not find) ? OS Brian O'Connor wrote: Background removal is verbotten! Brian O'Connor From: Olga Smirnova [mailto:olga.smirn...@hw7.ecs.kyoto-u.ac.jp] Sent: Wed 4/03/2009 2:14 PM To: rietveld_l@ill.fr Subject: cRs Dear All, How is life with conventional R factors when you always have to divide by zero background? Let's have time. Considering a part of the profile without peaks one gets 100% cR. I did not give the agreement factor; I would say those cR with all non-excluded points is incorrect, but cR for points with Bragg contribution is almost the same! Do you decrease the Rs by adding the background or do you increase cRs by subtracting the background? OS PS I did not ask my supervisor before sending such a mail. Internal Virus Database is out-of-date. Checked by AVG. Version: 7.5.519 / Virus Database: 269.21.6/1323 - Release Date: 3/10/2008 11:07 AM
RE: Anisotropic peak broadening with TOPAS
Sorry, pressed the wrong button... If you just want to try fitting the peaks, you could try something like this: str phase_name Metal_oxide local broad 100 'crys size for hk0 and hkl local sharp 2000 'crys size for 00l local csL = IF (And(H == 0, K == 0, L 0)) THEN sharp ELSE broad ENDIF; CS_L(csL) 'insert remainder of structure... I don't know much about Lvol, but isn't an average crystallite size for a highly asymmetric crystal not all that meaningful? I am willing to be educated here, as I haven't had much need to get accurate crystallite size from diffraction data before Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] -Original Message- From: Frank Girgsdies [mailto:[EMAIL PROTECTED] Sent: Wednesday, 29 October 2008 22:05 To: Rietveld_l@ill.fr Subject: Anisotropic peak broadening with TOPAS Dear Topas experts, 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 one for the a- and b-direction. The Topas Technical Reference, section 7.6.3. gives a similar example of a user defined peak broadening function, depending on the value of l in hkl. I could probably come up with an analogous solution which has a 1/cos(theta) dependence and two parameters, one for the 00l and one for the hk0 case. My problem with this approach is how to treat the mixed reflections hkl. I suppose they should be scaled with a somehow weighted mix of the two parameters, where the weighting depends on the angle between the specific hkl and the c-axis. However, I no idea how a physically reasonable weighting scheme (and the corresponding Topas syntax) should look like. -- Frank Girgsdies Department of Inorganic Chemistry Fritz Haber Institute (Max Planck Society) --
RE: Quantitative analysis
Hi Blaise In Bragg-Brentano mode, sample spinning does nothin for PO. This is because the diffraction vector is normal to the sample surface, and sample spinning rotates along this vector. Spinning does increase your particle statistics, which almost always helps. If you're looking at a capillary, spinning the capillary does help with PO, but just being in a capillary helps PO. As to spinning speeds, a good guide is one revolution per data point. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] From: Mibeck, Blaise [mailto:[EMAIL PROTECTED] Sent: Wednesday, 29 October 2008 01:25 To: rietveld_l@ill.fr Subject: RE: Quantitative analysis I am learning QPA and am worried about PO. I wonder why sample spinning isn't discussed more. I am luckily able to barrow time on a newer diffractometer with a sample spinner. Does this reduce PO? Or completely eliminate it? There is a set up variable in GSAS for whether you are spinning the sample - are there guidelines for how many revolutions to spin the sample if you just want to reduce PO? Thanks to all for there help!!! 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]mailto:[EMAIL PROTECTED] -Original Message- From: David L. Bish [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 28, 2008 9:09 AM To: Martin; [EMAIL PROTECTED]; rietveld_l@ill.fr Subject: RE: Quantitative analysis I agree that it's always best to avoid preferred orientation, but that is easier said than done on a routine basis. I have personally had good luck with the M-D PO correction on many known samples, as long as the PO was not severe. However, I imagine that Mario's problems are related to microabsorption in this case. Mario, if you can re-measure your data with a Co or Fe tube, it would be a good test of this. Dave Bish At 08:51 AM 10/28/2008 -0400, Martin wrote: Sorry to disagree. Experience tells me otherwise - the March-Dollase correction has nearly always led to poor quant results for me. It most certainly cannot be applied safely. Martin -- M Vickers Dept of Chemistry UCL Subject: Re: Quantitative analysis Date: Tue, 28 Oct 2008 02:53:20 -0700 From: [EMAIL PROTECTED] To: Rietveld_l@ill.fr 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_LAhttp://www.icct.ru/eng/content/persons/Sol_LA For the best free wallpapers from MSN Click here!http://wallpapers.msn.com/?ocid
RE: Beginer problems, difficulty charecterizing our diffractometer...
Couldn't the Al in the beam be due to beam spilling over the sample holder, irrespective of a spinning sample? . I'd also like to echo Lachlan's comment about Y2O3. It's what we use in our lab - if you can refine the thermal parameters to sensible values, you know you've got all of your intensity corrections done right. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] -Original Message- From: Leonid Solovyov [mailto:[EMAIL PROTECTED] Sent: Thursday, 18 September 2008 14:34 To: rietveld_l@ill.fr Subject: Re: Beginer problems, difficulty charecterizing our diffractometer... 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] mailto:[EMAIL PROTECTED]
RE: Sequence for varying parameters in FullProf
You might want to have a read of this paper: McCusker, L. B., Von Dreele, R. B., Cox, D. E., Louër, D. Scardi, P. 1999, 'Rietveld Refinement Guidelines', Journal of Applied Crystallography, vol. 32, no. 1, pp. 36-50. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] -Original Message- From: Palash Manna [mailto:[EMAIL PROTECTED] Sent: Tuesday, 27 May 2008 14:16 To: rietveld_l@ill.fr Subject: Sequence for varying parameters in FullProf Hi all, I am a newcommer in this field. Recently, I have started refining X-ray and Neutron data of Perovskite material using FullProf. I would like to know about the sequence for varying different parameters (like Biso, Bov, a, b, c, scale, zero shift, etc) and also, the logic behind the sequence. Thanks in advance and regards, -- Mr. Palash Kumar Manna Junior Research Fellow, Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085
RE: Preferred orientation?
_ From: Whitfield, Pamela [mailto:[EMAIL PROTECTED] The texture versus preferred orientation difference has some signficant blurry edges from a practical point of view. If you want it, it's texture. If you don't want it, it's preferred orientation! Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED]
RE: Analysis of data from instruments with theta-compensating slits
Patrick Do you mean like constant illumination length slit settings? Matthew Rowles -Original Message- From: Patrick D. Burton [mailto:[EMAIL PROTECTED] Sent: Sat 08/03/2008 5:54 To: rietveld_l@ill.fr Cc: Subject: Analysis of data from instruments with theta-compensating slits Reitvelders, I was wondering if anybody is performing Reitveld analysis on data collected using theta compensating slits. If so, what sort of intensity correction are you using? Thank you, Patrick Burton winmail.dat
RE: GSAS total beginner questions
Isn't GSAS able to handle XY data?? Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED]
RE: occupancy
Can you set up equations in FullProf? Refine the occupancy of Ti and set occ(Fe) = 1 - occ(Ti). Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] _ From: Igor Djerdj [mailto:[EMAIL PROTECTED] Sent: Wednesday, 5 December 2007 10:45 To: rietveld_l@ill.fr Subject: occupancy Dear all, The following question is addressed more to FULLPROF users. I want to refine atomic occupancies of Fe-doped TiO2 for instance. Assuming that Ti is substituted with Fe at some sites, how can I provide that the sum of occupancies of Fe and Ti is 1 or 100%? Regards, Igor Djerdj
RE: High temperature PXRD fitting in TOPAS
Assuming that your sample is stable over the temperature range, then the temperature will only affect the cell paramaters. (and maybe crystallite size) Allowing them to refine should be enough to allow for good fits. Cheers Matthew Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] _ From: sisir ray [mailto:[EMAIL PROTECTED] Sent: Friday, 16 November 2007 12:22 To: rietveld_l@ill.fr Subject: High temperature PXRD fitting in TOPAS Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir
RE: software request for calculating FWHM
Winfit isn't a bad program for getting peak paramters from individual peaks, and it's easy to use too! http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/krumm/Software/windows/winfit/ Matthew Rowles CSIRO Minerals Boc 312 Clayton South, Vic. 3168, Australia +61 3 9545 8892 -Original Message- From: Murugesan S [mailto:[EMAIL PROTECTED] Sent: Tue 09/10/2007 21:56 To: rietveld_l@ill.fr Cc: Subject: software request for calculating FWHM Dear All, How can i get the FWHM values for individual peaks of the powder sample data. I would like the FWHM values to the Williamson Hall plot. Any software is available for the getting of exact FWHM values from the powder data. Please give your suggestions and solutions. thanking you all, regards SM winmail.dat
RE: Density calculations for amorphous products
http://journals.iucr.org/j/issues/2001/02/00/ks0032/ks0032.pdf http://journals.iucr.org/j/issues/2001/02/00/ks0032/ks0032.pdf is the paper she referenced. Cheers Matthew Matthew Rowles CSIRO Minerals - Clayton Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED] _ From: Madsen, Ian (Minerals, Clayton) Sent: Wednesday, 3 October 2007 10:41 To: rietveld_l@ill.fr Subject: RE: Density calculations for amorphous products Dear Maria, We are also working on methods for determination of amorphous material. Can you please send me the full reference to the paper you quoted in your message. I urge great caution in the application of the Brindley model for correction of your QPA. Since the microabsorption correction is based on (MU - MUaverage)*R where MU is the linear absorption coefficient (LAC) of the phase and MU average is the LAC of the mixture and R is the particle radius. In your case MU and MUaverage should be the same (due to having the same/similar chemistry) and only differ because of packing density. Any difference in particle size may induce some microabsorption issues, but estimation of the correct value of R is problematic at best. The recent round robin on quantitative phase analysis highlighted the fact that while microabsorption is the greatest impediment to accuracy in QPA, misuse of the Brindley model frequently served to degrade, rather than improve, accuracy. Cheers o--oo0oo---o Ian Madsen Team Leader - Diffraction Science CSIRO Minerals Box 312 Clayton South 3169 Victoria AUSTRALIA Phone +61 3 9545 8785 direct +61 3 9545 8500 switch +61 (0) 417 554 935 mobile FAX+61 3 9562 8919 Email [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] o--oo0oo---o -Original Message- From: Fabra-Puchol, Maria [mailto:[EMAIL PROTECTED] Sent: Tuesday, 2 October 2007 7:46 PM To: rietveld_l@ill.fr Subject: Density calculations for amorphous products Hi all, I have a question concerning density calculations, I'm actually working on an amorphous phase quantification method using Rietveld and most part of the samples I'm working with contain high quantity of silica (amorphous and crystalline). I've attentively read the paper: Determination of the crystallized fractions of a largely amorphous multiphase material by the Rietveld method (X. Orlhac, C. Fillet,...) and I found out that the Brindley correction can be applied in my case. When I calculate the linear absorption coefficient of each phase I must to take into account also the amorphous phase, isn't it? . I just would like to know if someone could indicate me how to calculate this factor making difference between an amorphous and a crystalline phase (for example, concerning silica). I know the atomic absorption coefficient of each element must be multiplied by the packaging density in the case of powders but it just talks about the crystalline phases, what about the amorphous phase? Thanks for your help Sincerely, Maria Fabra Puchol Responsable Laboratoire Structures Structural Laboratory Manager - Saint-Gobain CREE 550 Avenue Alphonse Jauffret BP224 84306 Cavaillon Cedex - France tel: 00 33 4 32 5 09 36 fax: 00 33 4 32 50 08 51 e-mail: [EMAIL PROTECTED]
Re: More Caglioti U V W parameters
Just to add more fat to the fire Have a look at Young, R. A. Desai, P. 1989, 'Crystallite Size and Microstrain Indicators in Rietveld Refinement', Archiwum Nauki o Materialach, vol. 10, no. 1-2, pp. 71-90. (I can send the PDF if needs be) They talk about the Thompson, Cox and Hastings model, which explicitly separates the gaussian and lorentzian components of a psuedo-Voight peak shape. FWHM(G)^2 = U tan^2(T) + V tan(T) + W FWHM(L) = X tan(T) + Y/cos(T) As Prof. Stephens pointed out (and is stated in Yound and Desai), the coefficients can be broken into instrumental and sample (size, strain) components. U = U_inst + U_strain V = V_inst W = W_inst X = X_inst + X_strain Y = Y_inst + Y_size You can fix the instrument components with your standard, and then refine the difference with your sample. If you want to stick with the straight UVW symbolism, Young and Desai also state that you can use the size broadening term FHWM(G)^2 = Z/cos^2(T), which yields: FWHM(G)^2 = Z/cos^2(T) + (U_inst + U_strain) tan^2(T) + V_inst tan(T) + W_inst which can be re-written as FWHM(G)^2 = (U_inst + U_strain + Z_size) tan^2(T) + V_inst tan(T) + (W_inst + Z_size) as long as you constrain the two Z_size's to be the same. The last equation is what Prof Stevens alludes to in his refinement of U and W, all of the sample related parameters are folded up there. Of course, your mileage may vary... Cheers Matthew Matthew Rowles CSIRO Minerals - Clayton Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: [EMAIL PROTECTED]
RE: Instrumental broadening
Vahit This could be what you're after: Volume 109, Number 1, January-February 2004 Journal of Research of the National Institute of Standards and Technology Fundamental Parameters Line Profile Fitting in Laboratory Diffractometers R.W. Cheary, A.A. Coehlo J.P. Cline Have a look at papers by Cheary and Coehlo. They've done quite a bit of work on instrumental broadening (particularly on axial divergence) for their fundamental parameters approach. Cheers Matthew Matthew Rowles CSIRO Minerals - Clayton Ph: ᄉ 3 9545 8892 Fax: ᄉ 3 9562 8919 (site) Email: [EMAIL PROTECTED] -Original Message- From: Vahit Atakan [mailto:[EMAIL PROTECTED] Sent: Tue 26/06/2007 12:22 To: rietveld_l@ill.fr Cc: Subject: Instrumental broadening Dear all, In the book The Rietveld Method edited by young, (Page 114 chapter 7, part 7.2.3) five instrumental contributions were discussed. Broadening due to: 1) Source 2) Flat specimen 3) Axial divergence 4) Speciment transparency 5) Receiving slit I`m looking for a reference that has a figure showing the effect of each contribution on a peak. The explanation in the book is suffuciant but it would be better to see an image if there is any. Vahit winmail.dat
