Hi Armel,
A more extreme example was in Acta D56, 1549-1533 (2000) where a protein
structure (a new insulin phase) was solved by rigid body Rietveld refinement
from a synchrotron powder data set & subsequently confirmed by a single crystal
analysis (see Acta Cryst. (2001). D57, 1091-1100). NB: t
Liliana,
GSAS will refine the value of the absorption coefficient for neutron TOF data quite
easily (I recall one message of yours mentioned that your data was of this "flavor").
Just turn on the flag. Your Uiso's should rise for all atoms making those for the
heavy atoms positive. The ABS value
allel with single crystal analysis, is there an
accepted limit for R(F2) or any other parameter like
Rexp to follow? I'm using synchrotron data.
nandini
--- "Von Dreele, Robert B." <[EMAIL PROTECTED]> wrote:
> Nandini,
> GSAS gives R(F^2) which is sometimes defined for
> s
Jennifer,
Yes. Start with SXTLDATA to read in the hkl file. It will ask for lots of stuff but
you will only really need h,k,l,Fo & sig(Fo). Then go to EXPEDT to put in the rest of
the stuff (atom positions, etc.).
Bob Von Dreele
-Original Message-
From: Jennifer Anderson [mailto:[EMAIL
PM
To: [EMAIL PROTECTED]
Dear Dr Von Dreele,
The structure at room temperature was refined from neutron TOF. Now, I am using this
model to refine low temperature data from neutron CW. My sample has Cu-Cl-La-Nb-O.
Sincerely,
Liliana
-Original Message-
From: Von Dreele, Robert B. [mailto
Nandini,
GSAS gives R(F^2) which is sometimes defined for single crystal structure analysis. It
can be used in the same way as RBragg. Neither is statistically related to the
minimization process in a Rietveld least squares refinement, but can be a useful
diagnostic for the quality of the struct
Henry,
Do you have the correct polarization correction (POLA=0.95, IPOL=0) fro synchrotron
radiation? Did you just use the defaults for Uiso (=0.025)? If so that is too high for
something like HfO2 for which UISO might be closer to 0.004. Either of these would do
what you observe.
Bob Von Dreele
Donna (and anyone else who wonders about this),
In gsas\examples there is an iparm file (inst_xry.prm) that can be used for most any
Bragg-Brentano powder diffractometer. These instruments all perform more or less
equally independent of manufacturer with respect to the things of interest for
Rie
I would only add that much of the software development is done as a "hobby" by many
us, i.e. with only grudging institutional support.
Bob
-Original Message-
From: L. Cranswick [mailto:[EMAIL PROTECTED]
Sent: Fri 3/19/2004 3:44 PM
To: [EMAIL PROTECTED]
[hope this is not a resend - Ema
Hi,
According to GSASNEWS.TXT from July 6,1999.
"19. RAWPLOT now has the option for fitting positions, areas & shapes of up
to 30 individual reflections in a powder pattern using the same profile functions
available in GENLES."
GSASNEWS.TXT is part of the standard GSAS distribution and is in th
Hi,
There is a new version of GSAS for Windows. The Linux one will be out in a bit. Below
are lines from GSASNEWS.TXT with details of the new things & fixes in this version. In
brief, there is now conjugate gradient refinement, new tables of f' & f" for 10
standard wavelengths (CoKa fans can no
Dear Andrew,
You only need to constrain RM11 and RM33 to be the same for both phases; GSAS takes
care of RM22 by symmetry.
Bob Von Dreele
-Original Message-
From: Andrew Hector [mailto:[EMAIL PROTECTED]
Sent: Thu 3/25/2004 9:44 AM
To: [EMAIL PROTECTED]
I am trying to refine a magneti
Dear Andrew,
I should read your message a bit more fully. Maxim's response is of course correct.
One additional point is that you can only have one constraint for any GSAS parameter.
Bob Von Dreele
-Original Message-
From: Andrew Hector [mailto:[EMAIL PROTECTED]
Sent: Thu 3/25/2004 9:44
Andrew,
Still one more point - watch for the effects of damping on constrained parameters. I'd
remove any damping & then do your refinements. Also the constraints are on the shifts
in the parameters & not on the values. So if the values are different - they will stay
that way.
Bob Von Dreele
-
Dear Arie,
Some of this has been discussed earlier but in a LeBail refinement in GSAS the Ka1 and
Ka2 reflections are treated as independent and the 2:1 intensity ratio is not used.
This arises because of the severe computational difficulty of connecting the
intensities of these paired reflectio
.
Arie
On 30 Mar 2004 at 8:44, Von Dreele, Robert B. wrote:
> Dear Arie,
> Some of this has been discussed earlier but in a LeBail refinement in GSAS the Ka1
> and Ka2 reflections are treated as independent and the 2:1 intensity ratio is not
> used. This arises because of t
Dear Stephen (& others),
I know there have been a number of replies to this since P2/n does have an inversion
center which is positioned at the unit cell origin. However, if the space group is Pn
(or P2) then the location of the origin is arbitrary on one or more axes. GSAS does
"automatically"
ow it
is done. This way has one big advantage over user fixed origin -- it yields standard
uncertainties for all atoms and therefore for
all distances, etc.
Peter Zavalij
-Original Message-----
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 31, 2004 10:17
Stephen,
Whether the space group is centrosymmetric or not isn't the issue. The question is
whether it is polar or not. P2/n is not polar (i.e. origin defined relative to some
symmetry element) but P2 is polar (i.e y coordinate not chosen relative to a symmetry
element).
Bob Von Dreele
Ana (& others),
Find this option in the print options in the least squares control menu. The output
will list only those covariance terms >0.50 and <-0.50 (i.e. just the big ones). It is
a very condensed table with a variable name followed by variable names & covar. value.
Bob Von Dreele
___
Hi all,
There is a new version of GSAS for Windows; Linux to follow soon. The changes are:
GSAS News...
April 15, 2004 (tax day in USA)
1. A small cosmetic fix to the g-value editing routine.
2. There is now an option in histogram editing to set aside a certain fraction of the
profile points
To: [EMAIL PROTECTED]
Hello Bob Von Dreele and all,
I am Marcelo Gomes da Silva, PhD Student at PennState.
About this new version, is it avaliable for downlaod already?
If so, where?
Appreciate everybody's attention.
Marcelo
- Original Message -
From: "Von Dreele, Robert B
Title: Message
Hi
Folks,
There is now a new
Linux version of GSAS that matches the recent Windows version. Lots of changes
since the last Linux one. See GSASNEWS.TXT for details.
Find it at ftp://ftp.ccp14.ac.uk/ccp14/ftp-mirror/gsas/public/gsas/ in
the linux subdirectory.
As usual let me kn
Dear Marit (& others),
The current limit is 9 points - that's not your problem.
Bob Von Dreele
-Original Message-
From: Marit Stange [mailto:[EMAIL PROTECTED]
Sent: Thu 4/22/2004 9:36 AM
To: [EMAIL PROTECTED]
Hi,
I have a problem with a data file (SR-XRD data, 19400 points, 2theta; 3-
Jon,
I risk a public reply here. One possibility everyone should be open to is that a real
phase change has occured during some experimental manipulation of your sample. Some
phase changes are quite subtle and involve only slight (and at first sight) quite odd
line broadening. Higher resolution
Apu,
1. For now use the inst_xry.prm file in \gsas\examples.
2. POLA is appropriate only for X-ray data & not neutron data. GSAS knows the
difference.
Bob Von Dreele
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Mon 4/26/2004 11:45 AM
To: [EMAIL PROTECT
Dear Marcelo (& others),
GSAS should do texture (sph. harmonics) with "film" data (or image plate) powder data.
Image needs to be divided up in to 'pie' sections & integrated to give a sequence of
patterns about the azimuth. The read them as separate "histograms" in GSAS & give each
the appropri
Hi All,
There is a new version of Windows GSAS on the CCP14 web server. The biggest change is
that it will now do Pawley style extractions for one set of reflections from multiple
powder patterns. This is done inside GENLES. See below for note on this & other
changes. Linux & other versions will
Dear Doinita (and others),
I'm assuming this is a GSAS question. The tic marks show the ideal position of the
reflections according to Bragg's Law. The real peaks can be "out of position" for a
variety of reasons including a non zero ZERO. Most usually for ordinary x-ray powder
data the sample d
Dear Christoph (and others),
The constraints within GSAS are limited to pairs of parameters. You describe a
circumstance in which the total unit cell contents from a multiple atom sites is known
from stoichiometry; this is best handled with a "restraint". The restraints in GSAS
are not accessibl
Dear Darin & others,
The trick here is to realize the effect of the different site multiplicities.
Moreover, remember that the constraint applies to the shifts & not the values. So
start the site fractions with the right stereochemistry - you can put all Co in one
site & all Fe in the other with
I'd only add that given the clue that the peak in GaInAs is split from the PDF then
one should model it that way in a Rietveld refinement. It should agree. The thrown
away info in a Rietveld refinement is also evident in the Bragg peak intensities -
shows up as "funny" thermal parameters, low at
Jon & others,
Well, there is an attempt at this in GSAS - the "diffuse scattering" functions for
fitting these contributions separate from the "background" functions. These things
have three forms related to the Debye equations formulated for glasses. The possibly
neat thing about them is that
Marcelo,
Run REFLIST & request the file output of one phase of reflections to an ASCII file.
FWHM is the 7th column.
Bob Von Dreele
From: Marcelo J.G. Silva [mailto:[EMAIL PROTECTED]
Sent: Fri 8/27/2004 2:23 PM
To: Rietveld List
Dear all,
Even though I know t
Hi Folks,
Thanks to Brian Toby (see his note below) the various UNIX versions of GSAS and EXPGUI
have been prepared. I have placed copies of all of them in the GSAS CCP14 web site. As
he notes, please let me know of bugs in GSAS. He will deal with the EXPGUI ones.
Thanks,
Bob Von Dreele
Pam,
I hope that when you used GSAS you entered (as per instructions) "p 31 1
2" and not "p3112".
Bob
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Whitfield, Pamela [mailto:[EMAIL PROTECTED]
Sent: Monday, October 18, 2004 12:
Alan,
One of your operators is a typo.
"-x+y, y, -z+1/3" should be " Y-X Y 1/3-Z"
Bob
From: alan coelho [mailto:[EMAIL PROTECTED]
Sent: Mon 10/18/2004 3:16 PM
To: [EMAIL PROTECTED]
Pam,
As a developer and someone who uses other software to test a
eal Road
Ottawa ON K1A 0R6
CANADA
Tel: (613) 998 8462 Fax: (613) 991 2384
Email: <mailto:[EMAIL PROTECTED]>
ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca
-Original Message-----
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: October 18, 2004 4:39 PM
To: [EMAIL PROT
Try the GSAS Manual - a lot is in there.
Bob Von Dreele
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Thu 11/4/2004 10:19 AM
To: [EMAIL PROTECTED]
Hello !
I need papers about the mathematical aspects of Rietveld refinement.
In my countyr (Colombia) t
Dear Donita,
I'm sure you know that the vanadyl (V=0) bond length is short - you could put in a
restraint on its length as one possible control on your refinement. If their sites are
partially occupied then make sure you have a constraint to make FRAC(V)=FRAC(O). I
don't particularly understand
Dear Dan (& everyone else),
They probably can to some extent. Since the "rigid bodies" in GSAS can have
refinable internal coordinates they might be suitable for this kind of work. It
might take some imaginative design for the refinement in how the octahedra are
described so you should think on
Hi,
I'll be placing a new Windows version of GSAS onto the CCP14 web site
immediately. The fixes are noted below. As usual thanks to all, especially
those who find bugs & errors.
Bob Von Dreele
Nov. 13, 2004
1. Fixed problem in CW function nos. 3-5 (Finger, Cox & Jephcoat function)
where an od
please remove your "autoreply". It is not useful.
From: [EMAIL PROTECTED] on behalf of [EMAIL PROTECTED]
Sent: Sat 11/13/2004 2:37 PM
To: Von Dreele, Robert B.
[EMAIL PROTECTED]
Dear Ling Fei (& others),
GSAS requires all powder data to be records 80 visible characters long and each
terminated with an additional 2 characters (CR & LF). Thus, the length of the
file in bytes should be divisible by 82. CNVFILE will try to fix this; it does
not do any other formatting. Powd
interesting, one should try one's own name!
From: Armel Le Bail [mailto:[EMAIL PROTECTED]
Sent: Thu 25/11/2004 04:12
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Hi,
It seems that Google Scholar is a big support to
a more open access to the Knowledge.
There i
Riza,
Follow same procedures for your second phase. You will have to choose the phase
first in the map editing menu. FOURIER will only do one phase at a time though.
Bob Von Dreele
من: Riza Iskandar [mailto:[EMAIL PROTECTED]
تاريخ الإرسال: الثلاثاء 30/11/2004 08:
Larry,
Out of curiousity I downloaded a copy of DrawXTL (Windows version & source as
well). BTW still more work on the FCJ function. It had a bad habit of
misbehaving for reflections at exactly 90. deg 2-theta & tmp=0.0. It seems
that the choice of F=0.0 was a bad one (divide by zero crashes
Folks,
FYI.
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Peter L. Lee [mailto:[EMAIL PROTECTED]
Sent: Friday, January 21, 2005 11:32 AM
To: Mitchell, John; Jorgensen, James D.; Mark A Beno; Von Dreele, Robert
B.; Quintana
Title: Message
Hi
Folks,
A new version of
GSAS for Windows has been downloaded to the CCP14 web server. The changes are
relatively minor. They involve another "tweak" of the FCJ profile functions and
an update of the atmdata.dat file. See remarks below. Some remaining issues
are:
1) The Paw
Jools,
GSAS gives R(F^2)in the .LST file for each powder histogram assuming the
Fo extraction flag is "on" (default). Generally R(F) = 0.5* R(F^2).
Bob Von Dreele
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Jools [mailto:[EMA
Dear Yaroslav (and others),
Use cylindrical symmetry for flat plate Bragg-Brentano samples. There
isn't sufficient information in a single scan to do more than that.
Conseqently wnen you used mmm ample symmetry you got "nonsense"
(J=400!!). Use POLFPLOT option "A" to plot the resulting "axial
distr
Title: Message
Hi
Folks,
A new version of the
Windows GSAS has been placed on the CCP14 web site. The changes from the Jan.
27, 2005 version are relatively modest. These are:
Mar. 22, 20051.
Corrected some of the parameter names for the P. Stephens peak shape parameters.
These were mostly
Guys,
This appeared in a Rietveld e-mail a bit ago & needs a comment:
"While I can understand the general rationale for the idea (minimize the
weight of the very strong reflections to the final integrated intensity
for the reflection)"
The fact of the matter is that most least squares programs do
Title: Message
Well, when on a
roll...
A new version of
GSAS for Windows has been placed on the CCP14 web site. As you can see from the
notes below this has significant changes. The powder graphics has been improved
with a new font, a high/low resolution option and the availability of variab
Title: Message
A word
from a "provider" of a Rietveld code (please don't call me a "programmer").
"But if c>0.4 any
pV fails" - OK, for what fraction of the universe of "real world" samples is
"c">0.4? I suspect, given the general success of the TCH pseudoVoigt
function, that it is exceedi
Title: Message
Nic,
I know
about "super Lorentzians". Trouble is that many of those older reports were from
Rietveld refinements "pre TCH" and used a formulation of the pseudo-Voigt which
forced the FWHM of the Gaussian and Lorentzian components to be equal and
allowed the mixing coefficient
Title: Message
Nic,
This
is true for the internal math but the TCH function was assembled to reproduce
the true Voigt over the entire range of differing Lorentz and Gauss FWHM values
so it works as if the two FWHM components are independent. As for your question,
I'm not aware that anyone ha
Nic,
Well, I have been tempted from time to time to implement a "log normal" type
distribution in on eof the profile functions. A "nice" math description
ameanable to RR would help.
Bob
From: Nicolae Popa [mailto:[EMAIL PROTECTED]
Sent: Fri 4/15/2005 2:30 AM
To:
Alan,
Ah - the "rocks & dust" model. It works well.
Bob
From: alan coelho [mailto:[EMAIL PROTECTED]
Sent: Fri 4/15/2005 5:30 AM
To: rietveld_l@ill.fr
Nicolae, Nick, Bob, Leonid,
I have looked at many patterns (recorded by others) and a few cases have shown
Gerard,
Negative extinction is not physical - so has no meaning. There is some other
systematic effect that is affecting your result. BTW, I have recently used the
x-ray version of extinction in GSAS as well as the neutron (TOF) one on the
same set of samples. Both do work and both give about th
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" ma
Title: Message
Gerard,
In
GSAS there is a GENLES "print" option that will give the covariance terms larger
than +/- 0.5 in the list file. There aren't as many large ones as you might
think apart from the various background terms.
Bob
Von Dreele
R.B. Von Dreele
IPNS Division
Argonne Nati
Title: Message
Don,
As
Allen Larson noted GSAS only uses the 2nd setting for space groups that have two
(e.g. F d 3 m) so that he inversion center is placed at the origin. The eta
alumina structure you have is for the 1st setting. To convert from 1st to 2nd
subtract 1/8,1/8,1/8 from all xyz.
Title: Message
Hi,
A new Windows
version of GSAS has been placed on the CCP14 web site. There are some changes
since the Apr. 7, 2005 release. These are:
June 8, 20051.
Modified GENLES so that the Marquardt matrix modifier is changed before the
current cycle. It will decrease by 20% or less
John,
As was said by Francesco, you really must go back to the instrument
responsible for the diffractometer you used to collect the data for that
instrument parameter file. An old example of such a file is
\gsas\example\inst_tof.prm (the instrument doesn't exist any longer),
however iparm files fo
Use "R" option in REFLIST
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Dr. Yi-Ping Tong [mailto:[EMAIL PROTECTED]
Sent: Tuesday, May 30, 2006 9:55 AM
To: Rietveld BBS
software?
Dear all
Does anybody could tell me how GSAS
How about even lower angles?
From: Larry Finger [mailto:[EMAIL PROTECTED]
Sent: Tue 5/30/2006 4:25 PM
To: rietveld_l@ill.fr
AlanCoelho wrote:
> I would like to conclude that to be critical of a method such as the
> convolution approach to describing instrument
Could probably do much the same thing in EXCEL or some other spreadsheet
program, I suppose
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Jon Wright [mailto:[EMAIL PROTECTED]
Sent: Wednesday, May 31, 2006 8:54 AM
To: rietveld_
Hi,
Whoever is running the CCP14 site needs to capture these FAQ type
messages & stick them into the appropriate spot in the web site for
others to find later. This question (& ones like it) does come up
occasionally.
Bob Von Dreele
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne
uld anyone wish to contact the CCP14 or me!
http://www.ccp14.ac.uk/people/people.htm
Thanks
Richard
Von Dreele, Robert B. wrote:
> Hi,
> Whoever is running the CCP14 site needs to capture these FAQ type
> messages & stick them into the appropriate spot in the web site for
>
list
Page available via www.ccp14.ac.ukat
http://www.ccp14.ac.uk/solution/rietveldfaq.html
I hope this helps, suggestions or requests for the CCP14 site are
always welcomed and greatly received!
Richard
Von Dreele, Robert B. wrote:
> Hi,
> Whoever is running the CCP14 site needs
I need to note (again) that the file name extension for "raw" powder
diffraction data has no meaning within GSAS. GSAS does not care what the
extension is - most importantly the extension does not dictate how GSAS reads
the file. The file formats are described in the GSAS Manual and examples of
Sajeev,
There is a lot of information like this in the GSAS Manual.
Bob Von Dreele
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
Sent: Thursday, June 29, 2006 11:31 AM
To: rietveld_l
Stephanie,
The GSAS routine REFLIST has an option to produce a "single phase ascii" file
of reflections. One of the columns in that file is FWHM. Alternatively there is
a graphic in EXPGUI (widplt) that will plot FWHM and its Gaussian & Lorentzian
contributions as a function of 2-theta.
Bob Von
Pam,
Actually what was the issue with the cif files with multiple phases/data sets?
gsas2cif writes it out fine, I presume. Is it that the cif checkers can't
handle the complexity? I guess my comment is that they'd better as there is
going to be a lot more of this kind of thing in the future. Ev
Simon (et al.),
This is from the output of spcgroup with the antisymmetry option as 'Y'
Opr Iden -4z2z -4z3 2y M+-0 2x M110
Most of these are fairly easy to interpret
Iden = identity
-4z, 2z & -4z3 are the three parts of the -4 set of operations
2y & 2x are the two 21 screw axes &
I'd only add that powplot has an "A" option for producing an ascii file
with the as plotted values suitable for plotting by gnuplot (or anything
else). Key point - this file contains the as plotted data.
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Origi
ble, although more extra work has to be involved. I like the figure
powplot gives, but the only problem is the font.
Sincerely,
Ling Yang
-----Original Message-
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Tuesday, July 18, 2006 4:01 PM
To: rietveld_l@ill.fr
I'd only add th
Liz (& others),
A couple of points:
1) The format for the (default) "STD" GSAS powder data file has 10 values per
record in "I2,F6" (in FORTRAN speak) for each data point. Thus each entry can
be no larger than 99 (no decimal point is needed). The "I2" field is the
number of detectors used to
Dear Milinda,
In the menu for introducing the diffuse scattering function & setting initial
values (especially for "R" - interatomic distance), set the refinement flags
with "V" (as usual). If it didn't refine then your starting valued are not
good. Set A=1.0, R to an interatomic distance & U=0.
it possible to plot
a co-relation function from the diffuse background? I
mean, to obtain the correlations from the disordered
part of the structure?
Thank You.
Milinda.
--- "Von Dreele, Robert B." <[EMAIL PROTECTED]> wrote:
> Dear Milinda,
> In the menu for introducing th
el and the model from Bragg contribution are
co-related.
However, As far as I understand the GSAS model for the
total intensity is,
I(observed) = I(calculated Bragg) + I(diffuse)
In this case, the final model has two parts which are
completely independent of each other. Am I right?
Milinda.
Dear Apu,
Compilations of scattering factors in International Tables for X-ray
Crystallography go to sin(theta)/lambda = 2. Use those.
Bob Von Dreele
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAI
Dear Friedrich,
There are inequivalent reflections that overlap even in cubic
structures; those where h^2+k^2+l^2 are the same will have identical
d-spacings (e.g. 300 & 221, 410 & 322). Check through the list of
reflections to see those that have identical d-spacings; these are also
listed in the
Dear Franz,
I'm sure there will be many opinions on this but here goes from me.
The "sig" on the lattice parameters is only a measure of precision for the
value and is not directly related to the microstrain broadening. It is more a
measure of how well the peak positions can be collectively deter
Dear All (& Franz),
Use FXYE format. The positions given actually override those that would be
calculated from the average stepwidth given on the "BANK" record where it
matters. This scheme is only valid where the goniometer doesn't give truly
uniform steps but "jitters" about some average. Most
Hi All,
A couple of points about lattice parameter constraints:
1) Beware of using "damping"; it isn't needed especially for lattice parameters
in Rietveld refinements and it will mess up the intent of constraints if not
very carefully used.
2) The constraints are on the reciprocal metric tensor
run REFLIST and use the "R" option
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-Original Message-
From: Henry Hsu [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 19, 2006 12:07 PM
To: rietveld_l@ill.fr
Hi,
There are 3 new versions of the GSASkit on the ccp14 download web site.
The Windows version and two linux versions were created. The major
change is that the restrictive format requirements for raw powder data
files has been lifted. No longer are they read as direct access with
fixed length rec
However, the profile shape functions are not simple functions of Q but are
simple (Gaussian & Lorentzian) functions of 2-theta. Case closed.
From: Klaus-Dieter Liss [mailto:[EMAIL PROTECTED]
Sent: Wed 2/21/2007 4:03 AM
To: rietveld_l@ill.fr
Subject: Powder Diffra
OK, I did play about & display some Q-space (Q=2pi/d) plots in GSAS. It
will be an option in the next release. Pretty similar to conventional
2-theta plots - just a slight "squishing" of the scale at the upper end.
Might not be really desirable for complex patterns. Some TOF data where
data was col
Actually, I looked at Luca's little "show" & was sufficiently interested
that GSAS will now plot sqrt(I) style plots. There is one "problem" -
the value of "I" can be negative particularly after a background
subtraction. These must be suppressed to zero for this plot to work -
thus there is a small
I should add about cif is that there exists a number fundamental
incompatibilities between pdCIF & mmCIF. One main issue, as I understand
it, is that pdCIF naturally can describe multiple data sets (powder
patterns) used in a single structure analysis - mmCIF seems to forbid
this. This will cause t
Hi,
I have just down loaded 3 new versions of GSAS to the ccp14 web site.
These are for MS Windows, RedHat Enterprise 4 linux & Fedora 4 linux.
The last two are not interchangable as the former has more of the
libraries within the distribution. The changes are a) a bug fix for
gsas2cif and b) impro
Juske,
One point you should know the background in a TOF powder diffraction
pattern is not high - that is a nearly constant background multiplied by
a strongly varying incident spectrum which is much higher at short TOF
than at long TOF. Do a "divide by incident spectrum" and you wll see
what I mea
Hi,
A few important points:
1) Removing Ka2 from the powder pattern is not necessary for running GSAS (or
Fullpoof for that matter). Both represent the Ka1-Ka2 doublet quite nicely.
More important, most Ka2 stripping routines can adversly distort the data
messing up the result from a Rietveld re
Hi All,
New versions of GSAS for Windows and Fedora-5 have been placed on the CCP14 web
server. The changes are as follows:
May 2, 2007
1. A new record in the .EXP file has been defined:
'HSTnn NFOBS' the number of observed reflections for each phase in a histogram.
2. REFLIST now can prepare a '
er maps respectively? Sometimes huge
values are obtained for Patterson plot. Is there a way to normalized the
values, for example, to number of electrons/A^3? Many thanks.
Sincerely,
Ling Yang
-Original Message-----
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Thursday, May
Hi Everyone,
New Windows and Linux versions of GSAS have been downloaded to the CCP14
web site. The changes (since 2/2007) are:
June 12, 2007
1. A new record in the .EXP file has been defined:
'HSTnn NFOBS' the number of observed reflections for each phase in a
histogram.
2. REFLIST now can
Dear Stefan (& all, I suppose),
>From the original formulation by Caglioti, et al. U>0, V<0 & W>0 for a
"nonfocusing" neutron CW instrument and describes a parabolic curve with
the minimum at roughly the 2-theta angle that matches the monochromator
"take-off" (really 2-theta) angle. For a Bragg-Bre
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