On 17/01/2024 09:40, Reinhard Kleeberg wrote:
> "Automated mineralogy"
Dear Colleagues,
It sounds like there crisis for this community? I didn't see anyone mention the
AI story that was also in the news:
Hi Luca,
Thanks for sharing the links to your method - I hope we can try it the next time
we get stuck on identification.
It is a shame to hear you were delayed for so long by J.Appl.Cryst. Did they ask
you to cite some work from the Glasgow group as the commercial competitor? I
have in
Hi Matthew,
About the form factors : there is an active community doing "Quantum
Crystallography" or charge density analysis with the IUCr. Some of them have
been running a nice series of online lectures recently:
https://qcrwebinar.chem.uw.edu.pl/
You can find many experts there, and there
Maybe a silly question: are you assuming you have the data on an absolute scale
in order to do these calculations? Do things like surface roughness somehow not
matter?
Best
Jon
On 13/04/2022 11:56, Matthew Rowles wrote:
Thanks Tony
When I add the absorption edge correction to the
Dear Martin,
In addition to the other replies:
I am currently looking for a Python
xfab does this, see:
https://github.com/FABLE-3DXRD/xfab/blob/fd3015dbd4145daf6a471765887c3aa139eb8bab/xfab/tools.py#L1039
or C/C++ module
sginfo (https://github.com/rwgk/sginfo) offers a
If this rule is broken, such as the mode in
FIT2D that smooths patterns by pixel-splitting) then one introduces
correlation between points in the pattern
Hi Brian, your comment has triggered me it seems :-)
For SAXS and PDF it could be better to under-sample the data (see end),
but for
Hello,
I think it would be nice if I could cite some critical discussion, or
There are a couple of comments in the current issue of J.Appl.Cryst that
might be interesting for you:
https://doi.org/10.1107/S1600576719006575
Best,
Jon
Probably of interest to several readers here, a new paper on
methodology:
"Use of Bayesian Inference in Crystallographic Structure Refinement via
Full Diffraction Profile Analysis"
Chris M. Fancher, Zhen Han, Igor Levin, Katharine Page, Brian J. Reich,
Ralph C. Smith, Alyson G. Wilson & Jacob
3D whole pattern fitting has arrived:
http://dx.doi.org/10.1107/S2052252516001238
... and the samples are powders!
++
Please do NOT attach files to the whole list
Send commands to eg:
Dear Natale
A good quality powder pattern starts with a good quality powder. Using a
2D area detector is probably easier than trying to align a small sample
on a Gandolfi spinner, to increase grain statistics. Also a lower
resolution instrument will have fewer problems for grain averaging.
Hello
In the reference below they say they purchased 2-4 micron grain size
from Nilaco (perhaps it was:
http://nilaco.jp/en/order.php?DIR=CHEMIMENU=15CODE=FROM=14ITEM1=Diamond_PowderITEM2=Powder).
/J. Synchrotron Rad./(2014).*21*,
119-126[doi:10.1107/S1600577513028269
Dear Xiaodong, Jeremy,
Isn't it equation 3 here?
http://www.nist.gov/srd/upload/jpcrd488.pdf
f1/f2 are dispersion numbers and f'/f are the anomalous ones. The
relativisitic correction number for iron then shows up on page 221.
Best,
Jon
===
On 11/06/2015 17:27, Jeremy Karl Cockcroft
Thanks Davide for this useful initiative, I have joined. I don't doubt
the value of the Rietveld list but pictures are also useful.
It was recently bought to my attention that funding may be related to
public perceptions of research and for this reason we should pay
attention to things like
Powder Diffraction Discussion Group on facebook
http://www.facebook.com/groups/1087352967946225/
So from what I gather we have:
http://www.xrayforum.co.uk
http://www.reddit.com/r/crystallography
http://www.researchgate.net/topic/x-ray_diffraction
There are many other places where
On 2015-05-10 17:36, Alan Hewat wrote:
Jon... nicely illustrated... by posting an interesting link...
Thanks! Obviously I think these serial methods are a fantastic
opportunity for this community. An IUCrJ commentary by me is here:
Serial crystallography for the masses:
On 15/01/2015 12:15, Norberto Masciocchi wrote:
Il 15/01/2015 11:46, Fauth Francois ha scritto:
1- the data format of the input file your are using for your
refinement does not allow counts more than 10^6, This is typically
the case with GSAS input file format
Here at ALBA, as you
Dear James,
I'm not sure these are quite what you are after, but I'm suggesting them
anyway. There were several papers from Gordon Barr about non-parametric
methods:
SNAP-1D: a computer program for qualitative and quantitative powder
diffraction pattern analysis using the full pattern
On 06/04/2014 08:06, Leonid Solovyov wrote:
The faulting model in DDM gives nearly perfect agreement with the experiment:
http://sites.google.com/site/ddmsuite/home/Copper-DDM.png
It looks a little bit reminiscent of this pattern for ice:
http://www.science24.com/paper/15441
...but the
Jools,
To get the value more directly I think you can also measure the
scattering at two theta of 90 degrees in the horizontal versus vertical
plane. We did this last week at the synchrotron in the course of making
some detector correction files and there was a nice hole in the
diffraction
On 21/03/2014 10:59, Norberto Masciocchi wrote:
...
So, the question is:
Is there any way do get around this problem (without resorting to
spherical hamonics or to grind the specimen in a WC, SiC or BN mill)?
High energy X-rays or neutrons in transmission geometry would seem to help?
Best,
Did I click on the right link? The second point says:
Develop new experimental approaches and measurement routines as
required by a growing user base.
It doesn't sound so bad, unless the candidate can't think of any novel
experimental techniques to invent.
Jon
On 05/12/2013 19:02, Cline,
With a 2D detector you see spots for grains and smooth peaks for
texture. You can also observe a collection of grains which exhibit
texture giving a non uniform spot density. Usually by grains people
expect randomised changes in intensity with small orientation changes.
For texture there is a
On 31/07/2013 03:07, Leonid Solovyov wrote:
... There is a
widely scattered belief that restraints always improve not only the
restrained values, but also the “unrestrained” part of structure such as
intermolecular distances, orientations, planarity etc.
Apart from your word always, I
On 31/07/2013 17:25, Leonid Solovyov wrote:
One can make everything OK simply by choosing an appropriate weight
of restraints. The uncertainty in the restraint's weight appropriateness
makes every restrained refinement a know how.
Likelihood and/or the free R-factor offer routes to choose
Hi Alan,
I also find it hard to understand the rationale behind this approach.
G(r) can suffer from fourier truncation artifacts due to the finite q
range of the data, but there seems to be no such limitation in a model.
Isn't there a risk of fitting to truncation ripples with G(r)?
As for
There can be some value in comparing S values for different models with
the same data (eg ranking at least). A value much less than 1 (eg 1E-3)
indicates that you lost an esd column (or scaling factor) somewhere in
your data processing, and you should really try to find it again. Having
S2
sisir ray wrote:
How does the atomic displacement parameters (ADPs) works in TOPAS
Academic?
Typically adp is anisotropic displacement parameter, and describes
the rugby ball shapes atoms get in ortep pictures.
Are / there any litrature on unn /atomic displacement parameters ?
Thank you for
Martin wrote:
PS For anyone interested in an explanation of texture vs. PO, see:
http://pd.chem.ucl.ac.uk/pdnn/inst1/texture1.htm
http://pd.chem.ucl.ac.uk/pdnn/inst1/texture2.htm
I disagree! The web page has confused texture with granularity. See:
Davide,
Did you check for extinction and preferred orientation? Otherwise what
does a combined fit give? The difference of about 10 sigma suggests a
remaining systematic error. What is the impact of refining anisotropically?
Good luck,
Jon
Davide Levy wrote:
Dear All,
I have a
Hi there,
Since I just got the graphics card working again after a similar
upgrade, I'm feeling brave enough to try without wine (running).
$ file fp2k
ELF 32-bit LSB executable, Intel 80386, version 1, statically linked,
corrupted section header size
... which shows up on google/ubuntu
Phe,
Have you investigated the MFIT menu in fit2d? It should fit a series of
1D rows of the image to 1D peak shape functions.
Best,
Jon
On Wed, 4 Jul 2007, Phe Man Suherman wrote:
Dear All,
I have some ESRF data of diffraction from a single crystal thin film. The data
was recorded on
From http://www.iucr.org/iucr-top/cif/faq/
# What is DDL3?
DDL version 3 is the name given to some work in progress by Syd Hall and
his colleagues at the University of Western Australia. It is intended to
build on the greater consistency and data typing abilities of DDL2
without tying the
Klaus-Dieter was only proposing Q-scale plots for publishing results,
Why this 2pi factor? Why not 1/d or sin(theta)/lambda. During a very
brief look at SAXS it seemed at least a few authors disagree about the
units, with s also appearing sometimes. It was confusing and there was
a lot of
... The problems bothering me are
the measured peak is much wider than the simulation
Peak widths should be 400 microns (your beamsize) divided by 3.5 cm
(your distance) in radians, which is about 180*0.4/3.5/PI = 6.5 degrees.
HTH,
Jon
The next file I have to make is from a Topas analysis as well. I'm not
sure any other program could handle the constraints I constructed for
that one (how's that for being controvertial?!).
It might be very useful for any future reader of your cif file if you can
paste the topas inp file in
On Mon, 27 Jun 2005, Vikrant Chauhan wrote:
Hello everyone,
I am a novice crystallographer ( so to say )..workingon XPERT PLUS..can
somebody tell me where to look for notes on rietveld method (online) ..coz
wherever I look its all about some other programs for rietveld fitting ,
Of course, both are eventually linked, so the manner in which applying a
median filter to the 2-D image prior to producing a histogram affects
the whole procedure is what I was wondering about.
Make a radial transform (cake) BEFORE you apply any filters.
According to Jon's
comments, there
Least matrix is in the .CMT, according to the manual.
Alter the printing options in expedt to get it to print correlations on
the normal list file.
HTH,
Jon
On Tue, 30 Nov 2004, Sang-Heon Shim wrote:
Dear Experts,
This might be an FAQ. Where (in which file) can I find correlation
Bill,
Thanks! Exactly what I was after and I'd never have guessed it from the
title...
Jon
On Wed, 31 Mar 2004, David, WIF (Bill) wrote:
Hi Jon,
A lot of what you'll need is in the back of the International Tables Vol. A
in Chapter 15 which goes under the snappy title of Euclidean and
Asking purely as someone who once studied chemistry and has a selective
memory about boron; what is the compound you're looking at? I remember
things like (BH4)- and hearing about Wade's rules, but not isolated B-
anions. Isn't boron even less electronegative than carbon? Could you get
away with
At 05:51 PM 7/3/01 +0200, Luca Lutterotti wrote:
- only one type of peak is inside the program but the asymmetry is
handled in a much better way than in other programs (is a real
convolution as it should be) so I never found a pattern that I was not
able to fit very well with my function
Better to work with a single phase and use the red and black symmetry
operators, in my opinion. You might have to lower the symmetry for some
magnetic structures and add contraints on the positions accordingly, but
this saves a lot of headaches, even if it creates a few by making you think
about
Brian H. Toby wrote:
... SOAPBOXBesides, Q
is the Fourier conjugate of x (the coordinates); d-spaces have no
physical significance. D-spaces can mislead a novice into correlating
reciprocal space distances with real space distances./SOAPBOX
D-spacings are distances between lattice planes
The observations must be statistically independent, but need not be
independent in the sense of what they physically measure.
It seems implicit from that sentence that the datapoints must be physically
measuring some aspect of the model, is that the case? For example: Does a
Hamilton test on
Armel wrote:
And yes, the measurements have been done.
I would not call Science giving the MgB2 atomic
coordinates, already known.
Was this meant to be serious? Checking for any subtle structural changes
around Tc would be (has been?) a worthwhile investigation. Something easily
worthy of the
At 04:48 PM 3/29/01 +0200, you wrote:
You really think that MgB2 will give more ? Maybe... just routine to do so.
Armel, it was you who asked if boron was possible with neutrons, and when
you are told that it is, you say that anyway it is borin' (excuse the pun :-)
I hadn't realised there was
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