I can't resist adding one more to Mike's excellent list:
5. When peaks overlap strongly it becomes difficult to determine the
background level. Negative Uiso is a consequence of the background
refining to a value which is too low, especially where the peaks are
most dense in the pattern (short
On 31/07/2013 20:19, Brian Toby wrote:
To perform R-free with powder data, one must excise multiple complete
peaks from the pattern, say a few sections making up 10-20% of
pattern.
Hi Brian,
It is not so bad, you only need to throw in some peak intensities as
variables (a partial Pawley). You
On 08/08/2013 18:04, led15 wrote:
Is possible confirm the presence of delta ferrite in steel by xrd.
Yes: http://dx.doi.org/10.1007/s11661-010-0371-7
++
Please do NOT attach files to the whole list
Send commands to eg: HELP as the su
Dear Kurt,
You can peaksearch the images with any number of packages and then look
at the extracted spot positions. The stuff we wrote lives at
http://sourceforge.net/projects/fable/ and it is normally used to fit
grain-by-grain strain tensors. If you can isolate the spots you do
indeed get a l
Hi Alan,
In the limiting case of orienting all crystals in 3D you get a mosaic
single crystal (e.g. [1], or using an XFEL to measure 1 at a time). Then
the refined the crystal structure has somewhat better accuracy than with
a 1D Rietveld fit. Perhaps not the most popular idea for this mailing
Hello,
In the photo, the pellet is black and the powder is white. Why is that?
Best
Jon
On December 8, 2017 3:35:20 PM GMT+01:00, "François Goutenoire"
wrote:
>Dear Rietveld users,
>
>We observe an unusual asymmetric peak shape on pellet and not when the
>sample has been crushed in powder.
>
Hi Alex
I think conograph does well for tof.
Best
Jon
On April 13, 2020 8:24:55 PM GMT+02:00, Alexandros Lappas
wrote:
>Dear colleagues,
>
>
>
>We are working on some neutron time-of-flight (TOF) data and attempt to
>index them within GSAS-II.
>
>
>
>As the low-angle detector banks contain i
hed up into some spikes.
Horses for courses... shouldn't a fit show information which all has
approximately equal weighting in the minimisation algorithm? In the same
way that difference/esd is often more illuminating than just a
plain difference curve.
Jon Wri
ld try MI/X. The URL to download MI/X from MicroImages' is
http://www.microimages.com/ in the "Free Downloads" section.
Hope this helps,
Jon Wright
On Tue, 30 Mar 1999, Hongwu Xu wrote:
> Hi, Everyone,
>
> We have some neutron diffraction data collected and stored in t
r intensity or position. This fix
says that the systematic problems are really just random noise and
effectively increases the weights on the y_obs accordingly, giving larger
esd's.
Hope this helps,
Jon Wright
PS: See also GSAS/fullprof manuals and "Rietveld refinement guidelines"
lable as a beta
version. It appears you can assign the statistical weight to each pattern,
and in the example x-rays and neutrons are weighted equally. I'm wondering
what the best choice is. Each observation comes with a statistical weight
from the experiment? Isn'
Renyang,
Your best bet is to log into isis and read the data back into genie, then
write it out using gsasgen.
Something like the following will read your data in (check with the
instrument scientist, it depends on you login.com file as to which
commands you need and what works) :
>> lo w1 myfil
oday. Incidentally does
anyone have an example of a refinement where parameters are degraded by
the combined fit *and* they agree with each other when two separate fits
are carried out.
Jon Wright
PhD Student, Chemistry Dept, Cambridge Uni, UK.
On 25 May 1999, Andrew Wills wrote:
> Alan,
ing combined fits anyway?
Apologies to the list if I am displaying my ignorance, sometimes it's the
quickest way to learn.
Jon Wright
PS: Sorry to pick at your comments Paolo, it's a shame I'm not at RAL at
the moment. Could have discussed it out over a coffee...
a neutron expert might look on this as an systematic error
in the x-ray model :) Maybe not if one looks on the x-ray refinement as
fitting of the electron density function, rather than the nuclear
positions. For bonding studies it is the differences which are of
interest!
Jon Wright.
PS: Any offers
On Thu, 16 Sep 1999, Dr.Joerg Bergmann wrote:
> (high systematic error, bad difference plot, but low e.s.d.'s)
> (low systematic error, good difference plot, but high e.s.d.'s).
Apologies for diving off onto the general case, but does this make sense?
You improve your model and the quality of y
There are two programs which spring to mind. GSAS and Fullprof both allow
you to simulate neutron data. GSAS only does commensuate magnetic
structures. See www.ccp14.ac.uk for link to the programs.
Jon
Dept. of
Lachlan,
You can get hold of the freely available CCSL code from your site and
compile programs tf112m etc for doing TOF neutron Reitveld fits with
magnetism too! Compiles with the free g77 compiler after some minor
changes. All code is there, I have compiled and run it on a PC and
presented the
> On Thu, 23 Sep 1999, Ed Cussen wrote:
> > We're forced to use CCSL for the superior peak shape description and
> > so simply changing refinement program is not an option. I'm sure
> > that this problem must have been encountered before and I'm suprised that
> > there's not a 'standard' solutio
> ... not at all for magnetism, ...
Ahem, magnetism - resolution is very useful, in certain (rare) cases. I
guess that magnetic structures are not Armel's primary interest
but in at least one case resolution was essential. (FeAsO4 from IRIS (TOF
neutron) dataset, J.Phys:Condens.Matter 11 (1999) 1
generators. Is this possible with fullprof or would I run out of matrices
there too?
Thanks for any hints,
Jon Wright
--
>From international tables Fd-3m has a subgroup F 1 -3 2/m, which is a non
standard setting of R-3m. I get the following output from expedt:
Enter space group symbol
st squares matrix rather than the real
space unit cell parameters? I haven't picked up yet on why the derivatives
cannot be converted from w.r.t A* etc to w.r.t a etc. Is it just a time
saving?
Thanks
Jon Wright
On Fri, 7 Jan 2000, Armel Le Bail wrote:
> 15mn for checking a crystallography set is about my
> performance too.
Just out of interest, how long does it take people to pick up the
error in entry number 17280, attached below. It's just a cell
transformation from the cubic spinel [a->(a+b)/2, b->
On Mon, 10 Jan 2000, Armel Le Bail wrote:
> The number of papers published in crystallography which
> have incorrect space group or cell choice are quite numerous.
> Databases should show exactly the same number (5-10%
> or even more ??).
But isn't one of the values of a database that it should
On Mon, 10 Jan 2000, Jaime Alamo wrote:
> >PS: Has anyone found the error in that Fe3O4 entry yet?
>
> I think, It lacks the sqrt symbol, so ...
>
> [a->(a+b)/sqrt(2), b->(a-b)/sqrt(2)), c->2c]
>
> Also, it yields a negative setting that is less important.
?? I'm thinking of vector a b c,
me out right
when absorbtion is taken into account. So absorbtion is only a problem
when the peaks disappear.
Hope this helps,
Jon Wright
PS: Can anyone tell me if sigma_abs goes as 1/v for Gd?
Dept. of Chem
Asymmetry is discussed in:
J.Appl.Cryst (1984) 17, p.47 - van Laar & Yelon (+ ref's therein)
The above method is implemented in:
J.Appl.Cryst (1994) 27, p.892 - Finger, Cox & Jephcoat.
and source code for this peakshape is available. (They also talk about
secondary monochromators).
Hope th
e (with an low angle
asymmetry correction) would be also be appreciated.
Thanks in advance,
Jon Wright
Dept. of Chemistry, Lensfield Road, Cambridge, CB2 1EW
Phone-Office 01223 (3)36396; Lab 01223 (3)36305; Home 01223 462024
Alex,
There's something below which might help you. You'd need to set up a
refinement with a .exp file and a .raw file with the same root name (eg
fit.raw and fit.exp). The batch file then takes two arguments, the data
file name (eg run1.raw) and the root of name of the .exp file (eg. fit for
fit
Hi all,
Does anyone know if there is a quick way of getting at a background
subtracted r-factor within GSAS? (Without wishing to start a discussion
about why I might want one) Thus far the only idea I've had is to
calculate it by hand from hstdump, but that appears to be listing the
background as
being applied to data before presenting it for
refinement, which sounds ugly. Fullprof has a flag for transmission
geometry, hence my question.
Thanks in advance,
Jon Wright
PS : If someone could refer me to simple derivatio
On Tue, 8 Aug 2000, Brian H. Toby wrote:
> Brian Mitchell wrote:
> >
> > I have recently installed Windows NT on my laptop and find that the GSAS
> > graphics plot takes an excessive amount of time to appear. I did not have
> > this problem with Win 98.
> >
> > Any help/advice appreciated.
>
>
Paolo,
On Fri, 15 Sep 2000, Radaelli, PG (Paolo) wrote:
.
> Finally, here is a question for Bob and Juan. To me, it would be much more
> natural to remove Vo from the scale factor, that is to redefine a new S' so
> that
>
> Y=S'*L*A*E*|F|^2/Vo^2 and S'=K*Ltot*f
>
> This way, the scale fa
In comparing refinements with different powder datasets there is no
"number of observations" in common usage and no 10:1 rule of thumb.
Broadly, this means "crappy" data with a chemically unreasonable model
can sometimes give much better figures of merit than a good structure
with "good" data.
> Like Rp, Rwp, Chi2, RB are respectively from 3.96, 5.33, 2.68, 5.80
> to 3.35, 4.42, 1.85, 3.07.
This should pass a test of statistical significance. That does not mean
it really is preferred orientation, but if it is not preferred
orientation, then you
With all the file converters floating around, what are the chances that we
are going to proliferate files with corrupted formats? I have gotten some
files already that were supposed to be "GSAS files" but didn't have 80
columns, had blank lines, etc., and I assume they were made by file
converter
Ozhan Unverdi wrote:
Could someone give me the magnetic scattering factors of Ru+4 please?
www.google.com searching for "Ru4+ magnetic form factor" gives 17 results.
One of them is Sidis et al, "Evidence for Incommensurate Spin
Fluctuations in Sr2RuO4", Phys. Rev. Lett (1999) 83, 3320.
In
zhijian fan wrote:
*> Like Rp, Rwp, Chi2, RB are respectively from 3.96, 5.33, 2.68, 5.80
> to 3.35, 4.42, 1.85, 3.07.
This should pass a test of statistical significance. *
I made a hypothesis testing. H0: It needs not PO correction.
The model with PO correction:
G1=sum[wi
I am amazed by the flow of miss information that flows on this list whenever an
apparent problem with a space group comes up.
I asked a related question on sci.techniques.xtallography a few weeks
ago, but have yet to hear anything, misinformation or otherwise. If
anyone here can give me some
Nicolae Popa wrote:
the condition to not violate some elementary principles, in particular,
here, the invariance to symmetry.
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 const
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.
The (111)
>... to answer to your (too) long questions. May be later, OK?
Going back to this quartics versus ellipsoids peak broadening stuff,
maybe I can summarise:
Why should the distribution of lattice parameters (=strain) in a sample
match the crystallographic symmetry? If the sample has random, isolat
Is the fundamental parameter approach better than
mathematical approach used in most of the Rietveld
refinement programs?
Perhaps someone is about to explain the difference is between
"fundamental parameters" and anything else? I used to think it might
mean convoluting something which was actu
Freidrich,
Assuming you can use gsas2cif (or reflist or something) plus a text
editor to get an ascii file containing a column of peak positions then
in gnuplot I use:
top=0
bottom=-100
set bar 0.0
plot "hklfile.dat" u (n):(bottom):(bottom):(top):(top) with financebars
where n is the column in y
Well, that is an old chestnut that Cooper and Rollet used to oppose to
Rietveld refinement. I think Rollet eventually agreed that Rietveld was
the better method. Has Bill really gone back on that ?
The difference between the two approaches are just an interchange of the
order of summations wit
Bob,
This exactly what is needed when the sample is a mixture of amorphous
and crystalline components. But what happens when the material is a
single crystalline phase with some coherent defects? Don't the defect
<-> average structure correlations start to dominate, and separating
components is
Alan,
The "planned plugin architecture" sounds interesting. How concrete are
the plans? I'm interested in auto-generation of restraints for proteins
and fourier mapping at the moment...
Regards,
Jon
alan coelho wrote:
Dear all,
An academic version of BRUKER-AXS TOPAS is now available to
degree-g
Alberto,
Check you have the right polarisation correction. Synchrotron ~ 1,
laboratory typically 0.5 with no mono...
HTH,
Jon
Alberto Martinelli wrote:
Dear all,
I've got a problem with the Rietveld refinements of synchrotron data.
I'm using Fullprof and the problem is that the overall B, and t
Alan wrote:
BTW, Google.com ranks ILL WWW pages 3rd worldwide, in both Condensed
Matter and Crystallography, ahead of IUCr. To see what this means in
practice, try a Google search on inorganic structure :-)
http://rankwhere.com/google-page-rank.php?url=www.ill.fr
www.ill.fr has Google PageRank 7
Hello everyone,
Has anyone else noticed that sometimes when comparing two models Rwp is
better for one and R(F^2) is better for the other? The case I am looking
at is spacegroups P3 versus P-3, with the non-centrosymmetric structure
having more degrees of freedom and therefore very slightly bett
Gerard,
If you "strip" the K-alpha-2 using a monochromator, then you might get
better data. If you don't have that option, then fitting the data as
they come is probably a better approach, as you don't run the risk of
introducing artifacts.
Jon
Gerard, Garcia S wrote:
Dear everybody,
How impo
Brian Toby wrote:
If the numbers are real values then they are not counts. They may be
counts per second or something else. One needs to have uncertainty
estimates for these intensities before one can do a meaningful
Rietveld refinement (with any code). Following the above procedure, by
multipl
Xianqin,
How did you calibrate the sample detector distance? For reliable
absolute cell parameters it is very difficult to get good data with an
area detector. One approach is to mix a standard material into the sample.
As a gross approximation for small angles (in radians):
sin(theta) ~ theta
Dear Bhuv
> pattern and I have corrected possible graininess with spherical
[...]
> The data I have collected is on a image plate (only one frame).
Not sure I understand? If you have a 2D image showing powder rings then
you should have some very good ideas about the level of granularity or
textur
Alex,
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), could you expand further on your level of success
and any analysis you have carried out on this plan?
The massive random spike
I did some tests on the profile of the first diffraction peak of LaB6,
where I added a secondary soller angle, since I used secondary
soller slits, and I added also the parameter for the horizontal
divergence in the equitorial plane. Finally I added a crystallite-size
parameter CS_L. I did the
Its best to use the terms axial plane and horizontal plane to avoid
confusion.
Alan, I'm confused! What do you mean by those terms? I thought "axial
divergence" was "beam hits different points along the two theta axis" -
is that a misconception?
Last point, what do you mean by vertical diver
I've attached a python script below which will convert a gsas rfl file
into shelx hklf 4 format - it assumes there is no peak overlap at all,
so it is *not* hklf 5 format and *not* suitable for refinement!
After installing python from www.python.org and copying the script into
your working directo
Bob,
Shelx's (3I4,2F8.2) for h,k,l,FoSq,sig is straightforward to do in
fortran but needs a custom number format in excel? Some people are able
to type:
awk "{printf(\"%4d%4d%4d%8.2f%8.2f\n\",$1,$2,$3,$8/100,$9/100)}" <
test.rfl > test.hkl
...and then delete the first and last line from th
Brian H. Toby wrote:
I am trying to convert a GSAS ESD file to a GSAS STD file
BTW, I would be surprised if FullProf does not have a way to input
intensities with uncertainties rather than assuming intensities are
counts.
Indeed it does! INSTRM=10 is x, y, sigma format for fullprof where it
I would like to know whether GSAS is able to constraint the Uiso value
so that it will be always bigger than zero.
As others have indicated - GSAS does not do that (topas gives you the
option, doubtless amongst others). Shelx does do that (with single
crystal data) and you can't turn it off
Sudhish,
See: J. Appl. Cryst. (1991). 24, 352-354
"Sucrose, a convenient test crystal for absolute structures"
R. C. Hynes and Y. Le Page
P2(1), a = 10.8631(9) , b = 8.7044(6) , c = 7.7624(7) Å, [beta] =
102.938(7)° at 300(1) K
Despite being great for availability, sugar crystals are freq
Let's say one gets a value of 0.1% strain.
=> width of the distribution of cell parameters in the sample
But on the other hand there are also the unit cell sigmas.
=> error bar on the average value of the cell parameters
How can one visualise this?
There is a distribution of cell para
Jacco,
I/sigma_I is a good idea in principle. It just looks ugly if you get the
sigmas right for certain instruments - there are meaningless steps all
over the place.
All of these problems of "what to plot" would go away if we all
submitted powderCIF files for our refinements. The "plot" cou
Hi Everyone; Just in case you don't follow ccp4bb or nature methods:
http://www.nature.com/nmeth/journal/v4/n3/full/nmeth0307-189.html
I thought that some of you might be interested that the journal Nature
has clarified the publication requirements regarding source code
accessibility. It is li
AlanCoelho wrote:
Not sure what to make of all this Jon
Don't shoot the messenger, I was surprised enough by it to forward it to
the list. I guess they imply if you want to keep all implementation
details secret you should be patenting instead of publishing? (Patents
seems to be free online,
Hi everyone,
Three responses saying it might be a lower spacegroup? I wonder if the
emperors have their clothes on today?
(006) reflections can't split in R-3c as they only have a multiplicity
of 2 in the first place (0,0,6 and 0,0,-6). You were lucky enough to
split (00l) which rules out an
Easiest is to click on the top corner of the plot window and select
options "copy to clipboard". Or directly write to gif via:
gnuplot> set terminal gif
Terminal type set to 'gif'
Options are 'small size 640,480 '
gnuplot> set output "test.gif"
gnuplot> plot sin(x)
gnuplot> set terminal win
Term
Is there not some significant prior art in iterative phase refinement by
an "FFT then flip" algorithm?
See for example:
Acta Cryst. (1996). D52, 30-42[ doi:10.1107/S0907444995008754 ]
"Methods used in the structure determination of bovine mitochondrial F1
ATPase" J. P. Abrahams and A. G. W
Did anyone look into the effects of using circularly polarised x-rays?
Just wondering...
Jon
Larry Finger wrote:
Franz Werner wrote:
Dear Rietvelders
Is it in principle impossible to determine the absolute structure from powder
data due to reflection overlap or is there a way via multiple w
Just a quick plug for a program called "chooch" which does a very nice
job of calculating f' and f" from an edge scan, see:
http://www.gwyndafevans.co.uk/chooch.html
For Fe/Cu then neutrons may help.
Cheers,
Jon
[...]
Each edge to be used is recorded, this allow to calculate using
Kramers-
If you can fit via a sum of a broader lorentzian and a narrower one it
may indicate the sample is a "mixture". Are you sure the sample is
microscopically homogenous?
Best,
Jon
Francois Goutenoire schrieb:
Dear Rietveld users,
I am currently working on Williamson-Hall graph in order to c
Hello Everyone,
Some reviews have just come out in the first 2008 issue of Acta A: 60
years of Acta Crystallographica and the IUCr:
http://journals.iucr.org/a/issues/2008/01/00/issconts.html
Start citing now for a nicely skewed impact factor in a few years time :-)
Happy Christmas,
Jon
Yetta Porter wrote:
Hello all, I am interested in finding software that can convert 2D
diffraction rings into 1D diffraction patterns AND allow phase/pattern
matching using the ICDD's PDF database. Currently, I am using Fit2D to
convert my rings to patterns and then Match! to phase match my pat
Works for me. Just fill out a BANK line with FXY or FXYE as described in
the manual :-)
Cheers,
Jon
[EMAIL PROTECTED] wrote:
Isn't GSAS able to handle XY data??
Cheers
Matthew
Matthew Rowles
CSIRO Minerals
Box 312
Clayton South, Victoria
AUSTRALIA 3169
Ph: +61 3 954
Kurt Leinenweber wrote:
... with wRp of 25% and crystallographic R also near 25% ..
Maybe the background is too low :-?
Jon
Alan Hewat wrote:
Many theoretical arguments about signal/noise forget that the
experimentalist has a finite time to collect his data :-)
The finite time to analyse and publish can also be rate limiting! In
this respect a high background is a fine addition to any instrument; it
gives a much l
Alan Hewat wrote:
Even if you have a low profile R-factor (due to a high background and a
low resolution pattern) the calculated standard deviations in parameters
can still be large, which gives me confidence in Rietveld refinement :-)
I hoped the values of esds come out similar to the ones put
William,
The "ELF" usually means it is the equivalent of a .exe file? Try:
chmod a+x setup_fullprof_suite ; ./setup_fullprof_suite
Something came up on the list a while ago about a upx issue. You
previously needed something like:
$ sudo apt-get install upx-ucl
$ upx -d fp2k
But perhaps thi
We have also limited the size of Rietveld list messages to 0.5 Kbytes
0.5 KBytes is only 512 characters? I would h8 2 c text message style
language as a consequence :-)
Best,
Jon
Won't you always be able to put a slightly larger atom if you let the
atom move up or down out of the trigonal plane? Anyway, it sounds like
you are asking for the largest circle which fits in the hole between
three circles who are touching (this is a 2D problem?). Try a google for
"Descartes C
radiated.
Any suggestions or comments are welcomed.
Thanks, Yetta
P.S. Let me know if you can't access the files (its in Bckgrnd
Subtr.zip), I'll send then to you directly.
--- In [EMAIL PROTECTED] <mailto:sdpd%40yahoogroups.com>, Jon Wright
<[EMAIL PROTECTED]> wrote:
Hi,
If you have the usual environment variables set :
GSAS=c:\gsas
PATH=...;c:\gsas\exe
PGPLOT_FONT=c:\gsas\pgl\grfont.dat
then it should all run from a dos prompt (run -> cmd or command.com). Or
at least, you can type "expedt", "powpref" and "genles" etc and the
programs run and even deal wi
Try this:
ftp://ftp.ccp4.ac.uk/ccp4/6.0.2/source/chooch-5.0.2-src.tar.gz
Best,
Jon
Jean-Marc Joubert wrote:
Hello,
I am looking for a program able to calculate f' and f'' from absorption
data for a resonnant diffraction experiment. I know that CHOOCH program
was able to do that. This progra
Dear Blaise,
A chi^2 of 500 means that on average your model is off by 500 sigma, or
500*500=25 counts. This usually means some technical detail has gone
wrong in file formats or weights.
If you don't manage to figure out the problem then if you can post your
refinement somewhere I am su
Markus Valkeapää wrote:
Any comments on these two different geometries here on Rietveld list?
It depends on the sample? Reflection geometry helps when there is a lot
of absorbtion.
Jon
You are warmly invited to attend a 3-day Workshop in Grenoble, which
aims at explaining the TotalCryst methods and demonstrating the FABLE
software package.
http://www.esrf.fr/events/conferences/TotalCryst/TotalCryst/
Please bring this to the attention of your colleagues. Registration is
open
Out of curiousity, I'm wondering, do many people use ionic scattering
factors instead atomic ones for Rietveld refinement?
Cheers,
Jon
Lubomir Smrcok wrote:
Just one question : have you asked your supervisor before sending such a
mail ? Though I understand your position it seems that you are
Dear Olga,
As you've noticed, the Rietveld R-factors tell you how well you fit the
pattern, but don't tell you how well you fit the peaks. There is a
correlated intensities R-factor which follows from the methods outlined in:
J. Appl. Cryst. (2004). 37, 621-628[ doi:10.1107/S0021889804013
Olga Smirnova wrote:
Did anyone try to calculate simple mean deviance and compare with
popular R factors?
OS
For "simple mean deviance" do you mean like in:
http://en.wikipedia.org/wiki/Deviance_(statistics)
Seems we normally call that "chi^2". If that's what you meant, then yes,
people do
Alan Hewat wrote:
... your name appears as ½¨²¨Áº
The problem is your mail reader, thunderbird displays some chinese
characters. Liang's mail correctly uses a MIME encoded word as the ascii
string:
=?GB2312?B?vaiyqMG6?=
Which means character set "GB2312" (chinese), "B"ase64 encoding, and
According to Caglioti relation, the dimensions of U,V,W are as (angle)^2.
Quick question - does anyone have a trick to stop the Cagliotti formula
going negative? Prodd currently has a habit of bugging out on a
sqrt(negative) and I'm wondering how other folks worked around that, or
if I've go
Alan Hewat wrote:
Jon Wright said:
Quick question - does anyone have a trick to stop the Cagliotti formula
going negative?
This can happen if the resolution is relatively flat, so that there is no
well defined minimum.
Seems to be the problem - also rather close to zero anyway.
if
Sounds like the parameter is the monochromator angle you would need to
use to convert an unpolarised beam into a beam with the polarisation
state you have (eg, 90 degrees gives 100% polarised). Don't confuse this
with the actual monochromator angle at the synchrotron, as the bean is
usually pol
Dear Alexander,
This is theoretically one of the few things that can be done with PRODD,
which is a refinement program based on the CCSL subroutine library. Some
multibank spiral structure refinements were done with the program when I
was doing my thesis.
1) How do I decide on the space gro
Hi Andrew,
A word on GSAS vs Fullprof:
GSAS can only handle a magnetic structure that can be defined by a unit
cell. So, your incommensurate structure would need to be close to a
lock-in value to work, i.e. (0 0 0.32) is close to (0 0
1/3).
While it is a lot easier to use a super cell, the
Just use mask polygon and draw a little triangle inside the pixel you
want to mask. It helps to zoom in first. (Usually it is easier to find
the hot pixels with a threshold mask anyway).
Best,
Jon
Yang, Ling wrote:
Hi,
Does anyone know how to mask single pixel in Fit2d? I found it neces
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