[Ifeffit] FEFF report: Hard tests failed in fovrg.

Bruce Ravel bravel at bnl.gov
Wed Aug 7 14:47:59 CDT 2013

Hi Matthew,

On 08/07/2013 03:35 PM, Matthew Marcus wrote:
> 2.    The later FEFFs use a different structure, in which the modules
> are separate programs.  Can this be integrated
> into Artemis?

I don't see that as a problem.  Demeter already does a lot of crazy
things, including playing around with the CONTROL values and replacing
Feff's pathfinder with one that I wrote.

> Going back to point 1, any "FEFF9L" would need to be a
> wrapper which executes the modules in correct sequence.

I doubt that Feff9L would be a drop-in replacement in Artemis, but if
Feff9L were a defined thing, then I (and other software authors --
yourself, for example) would have a defined target to work against.

> 5.    Is there some documentation showimg how FEFF(>6) is better than
> FEFF6L for EXAFS alone?  Under what conditions
> should we be dissatisfied with FEFF6L?

Umm ... well ... perhaps when fovrg fails its hard test? :)

> I know that FEFF9 has all kinds of nice things that it does, but
> many of these are irrelevant for Artemis use.

This is a recurring topic on this list and a most excellent question.
As I have written before, there is some anecdotal evidence that self
consistent muffin tins are an improvement in terms of the values of E0
needed for a good fit.  But I am not aware of a rigorous investigation
that has been published in any form (journal article on down to wiki

I think that simply having a version of FeffN (with N>6) in a form
that I can properly target in Demeter would be a real boon in that it
would be a lot easier to automate such tests.


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

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2
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  Upton NY, 11973

  Homepage:    http://xafs.org/BruceRavel
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