>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
>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
>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
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
>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. So
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,
Leoni
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
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
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
r 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.
>
>
>
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 00-0
>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 ri
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
***
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
***
- 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 refin
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 t
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
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, Krasnoyar
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
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
6600
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
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
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.googl
**
>
> Â
>
> - 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
.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 t
, 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
beta but downloadable from the Maud site (updated nearly every week or
two). But the old stable version works quite well anyway. And sorry if I
don't have all that time to maintain a fully featured site always updated
to the last news.
Best regards,
Luca Lutterotti
On Jun 26, 2013, at 1
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 RI
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 C
>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.
**
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 o
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
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
660
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 include
>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
h
>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.
*
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/
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
***
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
>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
_r
>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/s
>
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
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
eonid
***
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
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, IMH
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
>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
>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(
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
>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-O
>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 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.
For me
restraints are much more frightful ;-(:
http://www.google.com/search?q=restraints
While for
some sort of people they may be thrilling.
>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
>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 o
lovyov
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 Solovyo
*
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
From: Jonathan WR
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 u
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 crystallite
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,
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
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-an
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 h
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/So
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) crys
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 paramet
***
--- 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-
> beginne
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
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
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 w
ct: 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
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
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: T
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
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,
>&
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
D
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
*
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 fi
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
Inst
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
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 th
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 Technol
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
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
**
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 not
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"
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,
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
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
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
desc
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
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
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
Phon
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.
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 instrumen
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
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
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 cours
> 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 o
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
> 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 r
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