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

[Kevin Jorissen]

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