Just to put my bit in, I believe that the most significant advantage of higher
FEFF versions for EXAFS analysis is that it results in
more reasonable values for E0 for high-Z elements. I forget whether the issue
is high-Z scatterer or absorber. If you use any of the
common prescriptions for defining E0 with, say, Pt metal in FEFF6l, your fit
will want large values of enot. That said, I have not done
a real test by comparing FEFF8 and FEFF6 paths. Has anyone done that? It
would be interesting to know what happens if you simulate a
k^n*chi(k) with one program and fit it with the other.
mam
On 3/26/2013 1:10 PM, Ravel, Bruce wrote:
This is more a documentation bug in the sense that I have not written any
documentation explaining how to use Feff8 with Demeter. What's more, I have
not completely tested using Feff8 and there are probably still missing
features. I would not expect Feff8 to work completely to your satisfaction at
this stage.
Even once I get Feff8 support fully implemented, I have no intention of
distributing a copy of the Feff8 executable with Demeter. Indeed, I do not
have the authority to do so.
That said, you need to go to the File menu -> Preferences, the
Feff->executable. Change the value of that parameter to the location on your
computer where the Feff8 executable can be found. Demeter is not currently smart
enough to choose a Feff executable according to how you selected to generate the
feff.inp file. It is entirely up to you to do that correctly.
Feff6 input files often work, in some sense, with the Feff8 executable. Feff8
input files will not work with the feff6 executable. That is the issue you are
reporting as a bug.
In closing, I'll say two things. (1) Feff8 is not yet fully supported in
Demeter -- use it at your own peril. I will eventually get it fully
implemented, but it is at this time near the top of my list of priorities. (2)
You should go back to the mailing list archives and find the last discussion
about the relative merits of feff6 and feff8 for EXAFS analysis. I was then and
remain now rather unconvinced that feff8 does anything substantive for you in
the context of your EXAFS analysis.
B
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--
*From:* ifeffit-boun...@millenia.cars.aps.anl.gov
[ifeffit-boun...@millenia.cars.aps.anl.gov] on behalf of Devender
[dev...@rpi.edu]
*Sent:* Tuesday, March 26, 2013 3:26 PM
*To:* XAFS Analysis using Ifeffit
*Subject:* [Ifeffit] Possible bug in atoms files generation by Artemis
Hi,
I ran updater for Demeter 0.9.15. I was using Artemis to calculate paths for Bi
L3 in Bi2Te3. I saw now the option of using both (FEFF 6 and FEFF 8 style) for
atoms. Previously, I was using only available option of FEFF6 style. When I
tried to run atoms selecting FEFF 8, it generated atoms files but when I tried
to run FEFF calculations it produced following errors.
Error#1
" Unknown keyword: "EDGE" at line:
EDGE L3"
Error#2
"Unknown keyword: "exchange" at line:
exchange"
I worked around first error by replacing
"EDGE L3
S02 1.0 "- which was generated by atoms when FEFF8 style is selected.
with
"HOLE 4 1.0" and deleting Exchange keyword from feff file. After making
these edits in feff files, I was able to run FEFF without showing any errors. I have
attached all the files with appropriate name.
--
Devender
Graduate Student, Materials Science and Engineering
Rensselaer Polytechnic Institute, Troy, NY
Website <https://sites.google.com/site/devendermaun/>
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