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 <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

 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
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