[Ifeffit] Other programs than FEFF - GNXAS and MXAN

Bruce Ravel bravel at anl.gov
Sat Jul 29 22:42:44 CDT 2006

On Saturday 29 July 2006 17:24, you wrote:
> 4) The formalism underlying GNXAS is very elegant and reading the original
> papers is great. I suggest it is highly worth the effort.

This is true.  They are indeed very interesting papers.  The physics
or physical chemistry students reading this list would be well advised
to seek them out.

I would also put in a plug for the PRB from 1990 by Rehr and Albers
about the fast separable formalism for computing the photoelectron
propagator.  That paper was my constant companion for about a year in
grad school and is really quite lovely.

> 5) Regarding ease of use: is XAS amenable to a "black box" approach?
> Despite the fact that this clashes with what many of us teach to physics
> students, it might be very useful e.g. in the field of bioXAS. But can this
> be done? Or is the underlying physics too complex?

Ah!  The "black box" discussion.  That's a fun way to waste lots of
time. ;-)

The physics has its complicated parts, but I suspect that we have a
sufficient understanding of the problems.  There are many applications
where a black box is reasonable to consider and probably would even
work pretty well.  At the recent XAFS conference, the group from
Manchester, UK presented a high-throughput scheme that involves
automate processing of larfge quantities of data.  They seem to get
good results with minimal human intervention.  And Harald Funke gave a
really neat talk about Feff-based wavelets that could be a very useful
approach to a first-shell black-box.

There will always be a large part of exafs analysis that falls well
outside the scope the black box.  The sorts of crazy fits published by
some of the frequent contributors to this list (I am thinking
specifically of Scott Calvin and Shelly Kelly) will always defy

Well, that was my US$0.02 worth...

 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

 Molecular Environmental Science Group, Building 203, Room E-165
 MRCAT, Sector 10, Advance Photon Source, Building 433, Room B007

 Argonne National Laboratory         phone and voice mail: (1) 630 252 5033
 Argonne IL 60439, USA                                fax: (1) 630 252 9793

 My homepage:    http://cars9.uchicago.edu/~ravel 
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/

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