Hi Will:
The relationship between the data in k-space and R-space is described in this
tutorial:
https://docs.xrayabsorption.org/tutorials/Basics_of_XAFS_to_chi_2009.pdf
Take a look at what a Fourier transform does. In few words I'd say it doesn't
matter which representation of the data (k-spac
Hi Peng:
It might be helpful to understanding some of Matt's points regarding S02
transferability, Ei and energy resolution by looking at this paper.
Comparison of EXAFS foil spectra from around the world
DOI: 10.1088/1742-6596/190/1/012032
Kind regards,
Shelly
-Original Message-
Fr
Hello XAFS community:
I'm excited to let you know that we have an opening for beamline scientist
within the Spectroscopy group at the Advanced Photon Source. Please help spread
the word.
https://bit.ly/3iN7Ehe
Kind Regards,
Shelly Kelly
Spectroscopy Group Leader
Advanced Photon Source
Yah know,,,I'm wrong The last one is a triple scattering path with just two
scattering atoms. the leg part is right...
oops
SK
From: [EMAIL PROTECTED] on behalf of Kelly, Shelly D.
Sent: Wed 7/16/2008 11:45 PM
To: XAFS Analysis using Ifeffit
Subjec
Hi Eckhard,
The first slide also has problems. The first path is a single scattering path.
All the others are double scattering paths. The word "single", "double" and
"triple" are used to describe the number of atoms that scatter. The number of
legs is used to tell the difference between t
I'd like to add my 2cents worth about the mean square displacement term. I
wrote it up on the EXAFS wiki, since I like to say it over and over. see
http://www.xafs.org/Common_Mistakes
Shelly
From: [EMAIL PROTECTED] on behalf of Scott Calvin
Sent: Wed 7/16/200
Hi Joseph,
I have a book chapter that explains how the different k-weighting affect
the chi(k) data produced in the background removal. I'll send it to you
directly, so as not to fill up everyone's mail box.
Here is the reference for others that might be interested.
Kelly, S.D., Hesterberg, D.
Hi Lachlan,
The reason that you want to keep the total absorption less than 3 is because
the number of transmitted x-rays becomes small. I=I0 exp(-mu x). So for mu x
=3 the number of transmitted x-rays are 5% of the incident x-ray intensity. If
you have a lot of x-rays then you can measur
Hi Pei,
Another parameter that affects the curvature of the background is where you
choose E0 and kmin for the spline. Sometimes if you choose a value that is far
down the edge, like half the edge step height, then the background has to curve
alot to get through the edge region of the spectru
Hi Fenglong,
You can do the next part of the analysis in Artemis. I have a powerpoint
tutorial showing the different parts of Artemis on the xafs.org wiki.
http://www.xafs.org/Tutorials
It is called Basics_of_XAFS_analysis.pdf It is a bit dated now, but the main
points are all the same.
I r
Hi Eckard,
I realize that you have posted a message every month for about 3 months
in a row without any reply: Shame on us... I will try to answer some of
your questions and maybe that will help to get some discussion going.
The energy scale in feff8 is NOT defined as you would expect it to be
SDK> Hi Pei-chang, See below for some ideas.
To whom it may concern,
Bottom of Form
Dear Prof.;
Here have some questions about Zn doped LiNbO3 single crsystal
EXAFS fitting problem, we did the similar EXAFS absorption spectra
as you can see the attach reference paper Fig 7, that shows
doubl
Hi Paul,
I was hoping someone else would answer your question. I have an idea. It might
not be a good idea.
Look up the MSRD term that you get from Grant’s DFT parameterizations for the
first Zn-S bond. Play around with the Einstein model for a Zn-S bond of the
correct distance for t
> So what do you all think? Is it better to impose the somewhat
> arbitrary limit that Scott suggests in hopes that it will work as
> intended most of the time? Or is it better to leave things as they
> are, allowing you to import more data but running the risk of
> corrupting Ifeffit's memory ma
Hi Scott,
The change in frequency is a bigger affect at high k than the energy
shift parameter. The energy shift parameter affects the data more
strongly at low k. So I align the data to each other at low k, and then
they become out of phase with each other at high k. A similar effect is
seen
Hi Tony,
The approach that I like to take, is to vary the choice of E0 in the
background subtraction step so that the chi(k) spectra are well aligned
with each other and the theory. Then only one Ezero parameter is
needed.
Cheers,
Shelly
> -Original Message-
> From: [EMAIL PROTECTED] [
Hi Aaron,
In EXAFS the expected deviation in RCS(reduced chi square) is sqrt(2/nu)
So one fit is better than another fit if their difference is greater
than twice the fluctuation in the RCS values
(RCS1-RCS2)/RCS2 > 2 sqrt(2/nu)
We divide by RCS2 because our RCS-values are poorly scaled.
{in yo
.
>
> Dave
>
> >-Original Message-
> >From: [EMAIL PROTECTED]
> >[mailto:[EMAIL PROTECTED] On Behalf
> >Of Kelly, Shelly D.
> >Sent: Thursday, January 11, 2007 11:11 AM
> >To: XAFS Analysis using Ifeffit
> >Subject: RE: [Ifeffit] Projekt with
Hi Jens,
I believe the problem is related to the structure in the data before E0.
If you choose e0 to be at the beginning of the structure then the
normalization is handled better by Athena. Take a look at the attached
project file. The first data set with e0 on the edge as you would
choose for
Hi Jens,
You can try moving e0. E0 should be on the edge. Is E0 at the position
of the step? You could also send us an example. Then we can help more
directly. I'd guess that the step is caused by some background
parameters that are set incorrectly.
SK
> -Original Message-
> From:
Hi Todd,
One thing to try is to set s02 to a positive value and all the other
variables to reasonable values and then look at the real or imaginary
parts of the Fourier transform and also look at the chi(k) spectra. You
should "see" the affect that Scott mentioned.
Shelly
> -Original Messa
---
Shelly Kelly
Argonne National Laboratory
Bldg 203, RM E113
>
> On Saturday 06 January 2007 10:53, Kelly, Shelly D. wrote:
> > Hello Artemis users,
> >
> > I found an interesting feature in Artemis when generating a list of
> atoms
> >
Hi Lisa,
In general the R-factor is good if it is less than a few percent. The
value reported is 0.01 or 1% then the fit is satisfactory. Just as a
note the R-factor is calculated over the entire data range given by rmin
and rmax of the fit, so make sure that they are reasonable values.
To co
Hello Artemis users,
I found an interesting feature in Artemis when generating a list of atoms from
the attached cif file worth sharing on the list. In the attached cif file for
Pd2Si the position of the Si2 atoms are at x,y,z = 0., 0.6667, 0 with a
space group of p -6 2 m. Using this cif
Hi Silvio,
There are a number of ways to reduced the big spike at low k. Sometimes
just tweaking E0, kmin, kmax, and k-weight are enough.
My favorite approach is to use the model as a theory in the background
subtraction procedure. I talk about how to do that in this presentation
file that I p
Here is an edited version. I apologize.
Shelly
Hi Juan and John,
Here us my 2cents worth...
Unfortunately the magnitude of the FT is not as simple as a RDF. I agree with
John that the ultimate goal of the analysis is to come up with a RDF. But I
disagree about the worth of adding a bi
Oh crap, I didn't mean it like that.
SK
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Anatoly
Frenkel
Sent: Sunday, September 24, 2006 9:42 AM
To: XAFS Analysis using Ifeffit
Subject: RE: [Ifeffit] Phase corrected Fourier transforms
In the future, I r
Hi Juan and John,
Here us my 2cents worth...
Unfortunately the magnitude of the FT is not as simple as a RDF. I agree with
John that the ultimate goal of the analysis is to come up with a RDF. But I
disagree about the worth of adding a bit more processing to the spectra that
makes the spectr
Hi Juan,
I liked the rule. It motivated Scott to give a quick reply. And the rest of
us got a smile out of it.
Cheers,
Shelly
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:ifeffit-
> [EMAIL PROTECTED] On Behalf Of Juan Antonio Maciá Agulló
> Sent: Thursday, September 14, 2006
Hi Gerrit,
My web page has a couple of examples that I think you will find helpful.
Take a look at http://www.mesg.anl.gov/Skelly.html . The "Basics of
EXAFS data analysis 2004" presentation and the tutorial on background
removal for MoO3 will answer most of your questions. The alignment of
meas
Hi Bridget,
Here are some other things to consider.
1) Is the second oxygen shell really necessary? What happens when you
leave it out of the fit and remove 3 parameters? Whenever I "make-up" a
structure I always take the minimalist approach. If the
reduced-chi-squares for the two different m
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