ce of coefficients is explicitly stated.
Hence, if denote by Eij the components of the microstrain tensor in an
orthogonal coordinate system related to crystallite, then
the coefficients are some linear combinations (specific to every Laue class) of
the averages .
Best wishes,
Nicolae
and size can not be estimated better.
>the fit was quite better
> (especially in cases showing stacking faults, with directional effects
> hardly approximated by ellipsoids) but remained "phenomenological".
The thermodynamics is phenomenological science, have we to consider
rong staking faults effect? I would accept your challenge, but I'm not
sure that with a knife in place
of scissors is possible to do easy tailoring. That doesn't mean the knife is
good for nothing.
Best wishes and ... il faut pas s'enerver
Nicolae Popa
e. To not
risk the next examination probably he will not put this question: how then
you
searched for size anisotropy in CeO2 with ARIT? Or the symmetry
restrictions are optional?
Nicolae Popa
> Not violating symmetry restrictions you may either
> have the sphere with the terms 11=22=33 and 12=13=23=0
> or something else allowing the 12=13=23 terms to be equal
> but different from 0. These two possibilities are all you can do
> in cubic symmetry with h,k,l permutable. If I am not wrong.
>
> >(you could be a good boxeur, Armel!),
>
> Knocked out at round 4 ! Argh !
Some people believe that "fair play" is mainly an Anglo-Saxon apanage
(prerogative). Obviously they are wrong.
>
> Anyway, a sphere was good enough for the previous
> size-strain round robin... Hope that the next siz
> Dear Prof Popa,
>
> I had been meaning to implement the quartic form for peak width in a
> refinement program for some time, but did not figure out how to generate
> the constraints from a general list of symmetry operators. Is there a
> simple trick for doing this? I was thinking of just choosi
Doinitza, Doinitza, scuze fara rost. Cei mai multi folosesc GSAS, dupa cum
vezi Bob a mers la sigur.
- Original Message -
From: "Doinita E Neiner" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, June 28, 2004 11:35 PM
Hello,
I am so sorry, I have forgotten to specify that i
CNRS is wrong, but take into account that nobody is a prophet in his own
country
N. Popa
- Original Message -
From: "Armel Le Bail" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, August 23, 2004 1:38 PM
>
> >And he is modest as well :-)
>
> I have to be modest. Accord
ough robust and you can
expect to obtain accurate volume averaged column length as function of
direction.
Best wishes,
Nicolae Popa
>
> Jens,
>
> Your effect might be more related to strain than size broadening. You
> would have to check widths at various diffraction orders in
Don't worry, it is only funny. And now is funny even more (my opinion)
Nicolae Popa
> Dear Respected Sir,
> Have I done anything wrong! I am really scared, because I am not that
much sound in english.
> I wrote like that because I respect Prof. Armel very much.
>
> Please
. v35 (2002) 338-346 - self citation too).
Nicolae Popa
>
> >The diffraction alone can not decide. Significantly different "physical"
> >size distributions could describe equally well the peak profile
> >(J.Appl.Cryst. v35 (2002) 338-346 - self citation too).
> >Nicolae Popa
>
> Looking at your figures 6b
the same chat list. An
alternative, a diversification, does not mean automatically a disidence. Let
us not blurred a word very dear to people like me, rising and living most of
the life in a dictatorial regime.
Yours,
Nicolae Popa
ore fun with a size strain round robin on some
> complex sample (or even a size-only round robin not on a
> cubic compound ;-).
I agree entirely.
Best wishes,
Nicolae Popa
2) 35, 338-346,
"Sample 2". It is true that the specific peak profile (that can be
"superlorentzian") can not be found in no available Rietveld code. It is also
true that no development has been done for anisotropy. Not
yet!
Best wishes,
Nicolae
Popa
aused by strain and
size for all Laue groups in Rietveld refinement, N. C. Popa, J. Appl. Cryst.
(1998) 31, 176-180."
Could I be so stupid to say that such kind of works, including mine, are
nothing?
Best wishes,
Nicolae Popa
> gamma, or whatever we assume it to be. On the former, it is easy to see if
> observed profiles can't be successfully fit ("super-Lorentzian" peak
shapes,
> for instance), which means that the TCH peak shape cannot be used.
However,
> an assumption that physically broadened profiles (size and str
d to cancel one
week before from an unexpected family problem.
Keep in touch.
Best wishes,
Nicolae Popa
ogram must have an option for Bragg-Brentano to avoid this trouble,
ask the authors.
Good luck,
Nicolae Popa
> Hi everyone,
>
> I tried to use spherical harmonics incorporated in EXPGUI/GSAS for
> modelling a preferential orientation in my sample. I used a cylindrical
> sample sy
different with the strain profile caused by different types of dislocations,
possible mixed?
Best wishes,
Nicolae Popa
> Best approach is to develop physical models for the line profile
broadening and test them for their plausibility i.e. model selection.
>
> Good luck.
>
> Bes
uals for statistical mathematics.
Best wishes,
Nicolae Popa
> Hi,
> I pointed out that each model needs to be tested and their plausibility
determined. This can be achieved by employing Bayesian analysis, which
takes into account the diffraction data and underlying physics.
>
>
gt; deconvolution (or any
> > other sophisticated deconvolution method that can imagine) give the
> > answermuch precisely? Both, the least square and deconvolution are
> > ill-posed
> > problems, but the least square is less ill-posed than the
> > deconvolution. At
tructure of materials", Springer-Verlag.
> [3] Armstrong, N. et al. (2004c), "X-ray diffraction characterisation of
> nanoparticle size and shape distributions:--Application to bimodal
> distributions",
> Proceedings of the Wagga-Wagga Condense Matter Physics & Materi
tainly not, if the
programmer wish to use exclusively TCH and nothing else. Why? I don't know.
Note that TCH is an empirical profile that reasonably approximate a Voigt
function (not the tails) that contains an empirical constraint: that FWHH of
Lorenz and Gauss components are equal one to another and equal with that of
the whole psudoVoigt.
Best wishes,
Nicolae Popa
>Dear Nicolae, >Maybe ya ploho chitayu i
ploho soobrazhayu, but even after your>explanation I can't see a way to
calculate from the results of>fitting described in chapters 6
& 7 of JAC 35 (2002) 338-346. From such>fitting you obtain only
dispersion parameter c. Or I missed something?>Anywa
nzian
profiles were reported from a long time, only were interpreted as coming from
bimodal size distributions. And third, you see, people have difficulties to
extract size distribution from the Rietveld codes as they are at this
moment.
Nicolae Popa
A
word from a "prov
be
discounted in any discussion about the occurence of super Lorentzian effects
in real samples.
Bob
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-From: Nicolae Popa
[mailto:[EMAIL PROTECTED] Sent: T
Voigt) sample to see if a) the fit
is the same and b) the eta>1 was an artifact. Any takers to settle
this?
Bob
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-From: Nicolae Popa
[mailto:[EMAIL
Title: Message
Alan,
(i) but a sum of two Lorentzians is not sharper
than the sum of two pVs (Voigts)?
(ii) We fitted the exact size profile caused
by the lognormal distribution by a pV (for low lognormal dispersion) or by a sum
of maximum 3 Lorenzians (for large lognormal dispersion).
T
Bob,
A "nice" math. description amenable to RR exists, take a look at JAC(2002)
35, 338-346.
"Nice" because the size profile is described by a pV (at "regular" lognormal
dispersions) or by a sum of maximum three Lorentzians (at large lognormal
dispersions - those 3% that Alan spiked about). The b
Dear Leonid,
See coments below.
>
> Dear Nicolae,
>
> This arithmetic is clear, thanks, but since you did not specify this
> exact way of calculation in the paper it was not evident. There are
> several other ways of deriving , for instance: to calculate Dv from
> the inverse integral breadth a
Leonid,
The lognormal distribution for particle size is not my modeling
(unfortunately), but if you insist, let see once again your equations.
= Da + 0.25(DaDv)^0.5 and sigma = (Dv/Da - 1/2)/2
For lognormal distribution first equation becomes:
2=(4/3)(1+c)**2+(1/4)sqrt[2*(1+c)**5]
For c=0.05 we
Title: Message
Alen,
you right, as far as the profile
corresponding to a given distribution is accurately described, any
representation is good. Nevertheless, at comparative accuracies, it is not
better to use a representation with smaller numbers of parameters?
The profile parameters are fu
Buna Mateo (where from you know Romanian?),
I spiked about the "regular" Rietveld programs that operate in the space of
measurement.
Sure, FFT is a solution, but I'm not sure that is the best solution. Even
fast, the calculation of the profile by Fourier transform is longer than to
calculate by el
Title: Message
Alan,
But the analytical representation of the profile,
even by empirical functions, also helps in the analysis of Size/Strain you don't
think?
You don't agree with 3 Lorentzians even if they are
sharper than two pVs?
Probably is a reason that I don't see.
Concerning the num
n TCH
pseudo-Voigt this condition is explicitly given). In this case there is no
problem with the "deconvolution", that, in fact, is made between two Voigt
functions.
Best wishes,
Nicolae Popa
- Original Message -
From: "Jon Wright" <[EMAIL PROTECTED]>
To:
(self
citation) and other ref. cited there (Langford, Louer, Scardi (2000))
Best,
Nicolae Popa
- Original Message -
From: "Leonid Solovyov" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, October 21, 2008 10:04 AM
Subject: Re: question on size-strain analysis
Dear Maxim,
Gau
citation) and other ref. cited there (Langford, Louer, Scardi (2000))
Best,
Nicolae Popa
- Original Message -
From: "Maxim V. Lobanov" <[EMAIL PROTECTED]>
To:
Cc: "Дмитрий А. Павлов" <[EMAIL PROTECTED]>
Sent: Tuesday, October 21, 2008 9:20 AM
12 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
ns if the user is able to 'run' through the three steps
described in section 4.2.
but he must be very careful when comparing experimental data with these
calculations.
Best wishes,
Nicolae Popa
- Original Message -
From: "Leonid Solovyov" <[EMAIL PROTECTED]>
in the beam scattered j times and u
is the unit vector along the scattered beam j+1
Best wishes,
Nicolae Popa
- Original Message -
From: "Leonid Solovyov"
To:
Sent: Sunday, July 26, 2009 9:05 AM
Subject: RE: LP factor in the Rietveld refinement
In principle, th
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