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

Matthew Marcus mamarcus at lbl.gov
Wed Aug 7 15:03:03 CDT 2013

OK.  I still use old Artemis.  I haven't tried DArtemis, especially in terms of integrating newer
versions of FEFF.  Is the procedure for doing this documented somewhere?

The folklore, with which my experience is consistent, is that FEFF6L reqires large values of E0 relative
to the edge in order to fit when the central atom is heavy, such as Pt.  What I don't know is how the accuracy
varies with FEFF version.  I would think that the FEFF group must have made those tests, and they're probably
published somewhere in the many papers that have come out describing the newer FEFFs, but I'm too lazy to
search for them.

As for me being a software developer, I'm not about to screw with the excellent work you've done on
the IFEFFIT suite.  For one thing, that would require learning Python.

On 8/7/2013 12:47 PM, Bruce Ravel wrote:
> 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
> page).
> 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.
> B

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