[Ifeffit] Possible bug in atoms files generation by Artemis

Bruce Ravel bravel at bnl.gov
Wed Mar 27 07:44:51 CDT 2013

On Tuesday, March 26, 2013 01:21:58 PM Matthew Marcus wrote:
> 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?  

This is *exactly* my point.  Except, as Matt said, for the rather
limited, unpublished tests made by him and John many years ago, no one
has reported on a substantive test comparing the efficacy of feff6 and
feff8 for analysis of EXAFS.  (Of course, computation of XANES and
other spectroscopies is a different topic entirely.)

Perhaps I would be more interested in fully implementing use of feff8
in my software if someone would offer a better justification than "8
is a bigger number than 6".

FWIW, I agree with Matt that the multi-pole self-energies is a very
promising thing that could have a substantial impact on EXAFS
analysis.  But few of those who claim to want to use feff8 with my
software are actually computing and using the multi-pole

In any case, I do not have permission to redistribute feff8.  So, on a
very real level, this conversation is moot.


> 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.


 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
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