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

But what is the practical effect of these for users of Artemis? For instance, Artemis doesn't do XANES calculations. I suppose the improved XANES-region calculation may become relevant for EXAFS data taken down to low k, where it's essentially XANES. Ab-initio DWFs are certainly beyond the scope of Artemis fitting. That said, it would be nice to have an approximate means of linking the DWFs for MS paths with those of related SS paths. Anybody have any idea how to do that? One approach might be to assume independent atomic motions. What would be the benefit of the RPA core hole? Under what circumstances would one want to use it? mam On 8/7/2013 12:55 PM, Kevin Jorissen wrote:

Hi all,

I think that several of the points raised in the last few replies will be better addressed off-ML. (See above)

As for the benefits of FEFF9:

* calculation of potentials is more stable and more accurate * improved self-energy (-> better peak positions and widths) * ability to use high-quality ab initio Debye-Waller factors (this will currently be beyond the skill of many users, but will be semi-automated in an upcoming release of FEFF9) * alternative "RPA" core hole * ... and don't forget: * 15 years of ironing out problems

Cheers,

Kevin Jorissen

On Wed, Aug 7, 2013 at 12:47 PM, Bruce Ravel mailto:bravel@bnl.gov> 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

-- Bruce Ravel ------------------------------__------ bravel@bnl.gov mailto:bravel@bnl.gov

National Institute of Standards and Technology Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973

Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel _________________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.__gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

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