Leonid,
The lognormal distribution for particle size is not my modeling
(unfortunately), but if you insist, let see once again your equations.
D = Da + 0.25(DaDv)^0.5 and sigmaD = D(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
Nicolae.Maybe there's no need for a pseuod-Voigt / Lorentzian
basedapproximations after all.
all
the best
Alan
-Original Message-From: Nicolae Popa
[mailto:[EMAIL PROTECTED] Sent: Sunday, April 17, 2005 9:00
AMTo: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Alan,
(i
buna Nicolae,
Not only arithmetic, I think is clear that both R and c were refined in a
whole pattern least square fitting. A private program, not a popular
Rietveld program because no one has inplemented the size profile caused by
the lognormal distribution.
not sure no one did.. we're
Nic,
Thanks,it will take a while (as usual) to implement.
Bob
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Nicolae Popa [mailto:[EMAIL PROTECTED]
Sent: Sunday, April 17, 2005 1:27 AM
To: rietveld_l@ill.fr
Bob,
A nice
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).
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
Dear Nicolae,
I will comment only upon your last statement because the limitations of
your modeling are clear.
Well, I don't know where from you taken these formulae
but I observe that for spheres of equal radius, then zero dispersion,
you have:
sigma(D)=5D/4, different from zero!
First
Indeed you missed something. I presume you have the paper.
Then, take a look to the formula (15a). This is the size
profile for lognormal.
There is the function PHI - bar of argument 2*pi*s*R.
Replace this function PHI - bar from (15a) by the _expression
(21a) with the argument x=2*pi*s*R.
2005 9:11
AMTo: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Dear Bob,
If I understand well, you say that eta1
(super Lorenzian) appeared only because eta was free parameter, but if TCH
is used super Loreanzians do not occur?
Nevertheless, for that curious
: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Dear Bob,
Perhaps I was not enough clear. Let me be more
explicit.
It's about one sample of CeO2 (not that from
round-robin) that we fitted in 4 ways.
(i) by GSAS with
TCH-pV
(ii) by another pV resulted from
gamma
to
concentrate on strain, micro strain, surface roughness and then
disloactions
all the best
alan
-Original Message-
From: Nicolae Popa
[mailto:[EMAIL PROTECTED]]
Sent: Friday, April 15, 2005 9:30 AM
To: rietveld_l@ill.fr
Subject: Re: Size Strain in GSAS
Dear Bob,
Perhaps I was not enough clear
]
Sent: Thursday, April 14, 2005 9:11 AM
To: rietveld_l@ill.fr
Subject: Re: Size Strain in GSAS
Dear Bob,
If I understand well, you say that eta1 (super Lorenzian)
appeared only
, micro
strain, surface roughness and then disloactions
all the best
alan
-Original Message-
From: Nicolae Popa [mailto:[EMAIL PROTECTED]
Sent: Friday, April 15, 2005 9:30 AM
To: rietveld_l@ill.fr
Subject: Re: Size Strain in GSAS
adventures...
Yes, profiles can be approximated, but the question is not in
approximating profiles. The primary topic of the discussion is Size
Strain in GSAS. GSAS and most other Rietveld refinement programs use
TCH-pV profile function which provides the simplest and more or less
correct way
...
Yes, profiles can be approximated, but the question is not in
approximating profiles. The primary topic of the discussion is Size
Strain in GSAS. GSAS and most other Rietveld refinement programs use
TCH-pV profile function which provides the simplest and more or less
correct way
It is not exact what you say, ty ploho cital.
6 7 from JAC 35 (2002) 338-346 gives the size profile - formulae
(15a)
combined with (21,22)
or (20a) combined with (23,24). If you look carefully, these profiles
are
approximated by pseudo-Voigt or sums of 2 or 3 Lorentzians. These
Dear Nicolae, Maybe ya ploho chitayu i
ploho soobrazhayu, but even after yourexplanation I can't see a way to
calculate R from the results offitting described in chapters 6
7 of JAC 35 (2002) 338-346. From suchfitting you obtain only
dispersion parameter c. Or I missed something?Anyway,
ECTED] Sent: Thursday, April 14, 2005 7:14
AMTo: [EMAIL PROTECTED]Cc:
rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Dear Nicolae, Maybe ya ploho chitayu i
ploho soobrazhayu, but even after yourexplanation I can't see a way to
calculate R from the results offitting described
Hi all,
Well, I thought I'd weigh in on this with a discussion of an aforementioned
SRM project:
We are in the final stages of preparing an SRM for determination of
crystallite size from line profile analysis. Through the course of his PhD
work and NIST postdoctoral position, Nick Armstrong
April 14, 2005 7:14
AMTo: [EMAIL PROTECTED]Cc:
rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Dear Nicolae, Maybe ya ploho chitayu i
ploho soobrazhayu, but even after yourexplanation I can't see a way
to calculate R from the results offitting described in
chapters 6
gonne, IL 60439-4814
-Original Message-From: Nicolae Popa
[mailto:[EMAIL PROTECTED] Sent: Thursday, April 14, 2005 8:10
AMTo: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Right, is rare, but we have meet once. A cerium
oxide sample from a commercial company, c=2.8. I do
April 14, 2005 8:10
AMTo: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Right, is rare, but we have meet once. A cerium
oxide sample from a commercial company, c=2.8. I don't know if they did
deliberately, probably not, otherwise the hard work to obtain such curi
--Original Message-From: Nicolae Popa
[mailto:[EMAIL PROTECTED] Sent: Thursday, April 14, 2005 9:11
AMTo: rietveld_l@ill.frSubject: Re: Size Strain in
GSAS
Dear Bob,
If I understand well, you say that eta1
(super Lorenzian) appeared only because eta was free parameter,
8. The simple modified TCH model (triple-Voigt), used in most major
Rietveld programs these days, is surprisingly flexible. It works well
for most of the samples (super-Lorentzian is an example when it
fails, as well as many others, but this is less frequent that
onewould expect) and gives
adventures...
Davor
-Original Message-
From: Leonid Solovyov [mailto:[EMAIL PROTECTED]
Sent: Wednesday, April 13, 2005 12:11 AM
To: rietveld_l@ill.fr
Subject: Re: Size Strain in GSAS
8. The simple modified TCH model (triple-Voigt), used in
most major
Rietveld programs these days
Voigt function was able to approximate
quite different cases. Of course, that is not true in general.
-Original Message-
From: Matteo Leoni [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 29, 2005 4:59 AM
To: rietveld_l@ill.fr
Subject: RE: Size Strain In GSAS
Leonid (and others
:59 AM
To: rietveld_l@ill.fr
Subject: RE: Size Strain In GSAS
Leonid (and others)
just my 2 cents to the whole story (as this is a long
standing point of
discussion: Davor correct me if I'm wrong, but this was also
one of the
key points in the latest size-strain meeting in Prague, right
Hi,
Long text but not fully convincing. At least concerning my questions (still
posted at the bottom). I'm risking a hurry reply without reading all
references (including to be published and PhD Thesis).
See comments below.
that likelihood term is described by a goodness of fit, say chi-square
Leonid,
Could you, please, give a reference to a study where Dv and Da sizes
were derived from the parameters of pseudo-Voight or Voight fitted to
simulated profiles for various size distribution dispersions?
I did something better (I hope).. at the end of the mesg you find xy
data with a
Dear Matteo,
Thanks for the exercise.
From pseudo-Voight fitting I have got Dv=33A, Da=23A,
which gives the average size D=21A and the relative
dispersion c=0.28 (c = [sigmaD/D]^2).
However, I suspect that the actual values you used for the simulation
were D~30A and c~0.25.
Do I win the F1 GP?
Dear Matteo,
Thanks for the problem.
I have used pseudo voigt function to fit the peaks and finally used the program
BREADTH and obtained Dv=31 A, Da=18 A.
Please send me your simulation parameters, plots/calculations.
Regards,
Apu
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
Apu Sarkar
Leonid (and others)
just my 2 cents to the whole story (as this is a long standing point of
discussion: Davor correct me if I'm wrong, but this was also one of the
key points in the latest size-strain meeting in Prague, right?)
Your recipe for estimating size distribution from the parameters
done several times...
With a whole pattern approach and working directly with the profile
arising from a distribution of domains, in most cases you're able to
recostruct the original distribution without making any assumption on
its functional shape (after all, most of the information to do
Hi,
So, to resume your statements, by using Bayesian/Max.Entr. we can
distinguish between two distributions that can not be distinguished by
maximum likelihood (least square)? Hard to swallow, once the restored peak
profiles are the same inside the noise. What other information than the
peak
: www.du.edu/~balzar
-Original Message-
From: Leonid Solovyov [mailto:[EMAIL PROTECTED]
Sent: Sunday, March 27, 2005 12:49 AM
To: rietveld_l@ill.fr
Subject: RE: Size Strain In GSAS
On Friday 03/25 Davor Balzar wrote:
Paragraph 3.3 of the article
Hi,
Nick Armstrong has advised me he will in non-email-land for a week or so.
I'm sure he'll resume this discussion when he returns...
Jim
At 03:45 PM 3/28/2005 +0400, you wrote:
Hi,
So, to resume your statements, by using Bayesian/Max.Entr. we can
distinguish between two distributions that can
*
***
- Original Message -
From: Davor Balzar [EMAIL PROTECTED]
Date: Friday, March 25, 2005 7:05 pm
Hi Apu:
As everybody pointed out, there are better ways (for now) to do the
size/strain analysis, but GSAS can also be used if observed, size
Dear Apu,
I know I will start up a good debate here, but size-strain analysis
with GSAS is a non-sense. The program was not written with that purpose
in mind and in fact it does not contains the instrumental aberration
part of the broadening that is necessary for such computation.
Indeed
et. al. Journal of Applied Crys. 37(2004)911-924.
In that round robin results they have reported the size strain obtained from
GSAS.
I my case also when I am trying with GSAS, the diffraction pattern is fitting
well except the peak braodening. I think this brodening is due to small domain
size
Dear all,
I think the statement that one cannot do line-profile analysis using GSAS is
too strong. In principle it is possible to do some
size strain analysis using GSAS, if the instrumental profile is e.g.
sufficiently described previously
by the Thompson-Cox-Hastings (TCH) profile function
. Balzar et. al. Journal of Applied Crys. 37(2004)911-924.
In that round robin results they have reported the size strain
obtained from GSAS.
I my case also when I am trying with GSAS, the diffraction pattern is
fitting well except the peak braodening. I think this brodening is due
to small domain
Lutterotti
On Mar 25, 2005, at 12:55, Andreas Leineweber wrote:
Dear all,
I think the statement that one cannot do line-profile analysis using GSAS is
too strong. In principle it is possible to do some
size strain analysis using GSAS, if the instrumental profile is e.g.
sufficiently described
Hi Apu:
As everybody pointed out, there are better ways (for now) to do the
size/strain analysis, but GSAS can also be used if observed, size-broadened
and strain-broadened profiles can all be approximated with Voigt functions.
Paragraph 3.3 of the article that you mentioned explains how were
43 matches
Mail list logo
