[Ifeffit] Connecting Artemis to FEFF9.6.4

Sat Jan 11 23:01:13 CST 2014

Hi Bao and Bruce,

There has indeed been progress since FEFF6 -- the newer versions of the
program have new input options that the old program will not recognize.
 E.g., as described in the post Bruce linked to, we now generally use the
EDGE card rather than the HOLE card to specify the absorption edge.
 However the HOLE card is still recognized by the current FEFF9.  Someone
mentioned FEFF breaking support for older input files.  To the contrary I
expect FEFF6 input files to work smoothly with the FEFF9 code.  E.g. the Cu
example in the FEFF6 distribution works with today's FEFF9.  FEFF6 and
FEFF9 may produce somewhat different output for the same input file because
some internal defaults and algorithms have changed.

FEFF9 is not meant to be run through the GUI exclusively.  Many users
(myself included) love working from the command line, and that will always
be 100% supported.  The GUI is just another way to control the input file
and run the same compiled fortran executables.   Occasional users and users
unfamiliar with the command-line terminal (the majority of our users work
in a Windows environment) seem fairly happy with it.  But you can always do
the same thing by typing "feff" on the command line.

Our interface still consists of a single text file with 10-20 lines of
keywords with options; and then a list of x,y,z coordinates.  It's kind of
old-fashioned; if something fancier is needed, I'm willing to help or
translate it or show interested parties the code.

On to the physics:

I indeed expect that the improved self-energy (we call it MPSE, for
Many-Pole Self-Energy) would improve EXAFS for many (not all) materials by
shifting peak positions and correcting broadening.  Other improvements
might come from new options for Debye-Waller factors, TDLDA, or
self-consistent SCF potentials (I think some on this mailing may have
questioned the value of SCF potentials).  The thread referenced by Bruce
asks how well one would have to know the dielectric function of a material
(that in itself may not be known very precisely) in order to get an
advantage from the MPSE.  In my own calculations a primitive built-in model
requiring no knowledge from the user already seems to provide some of the
improvement.  It's not a conclusive answer, but it's encouraging.  My
personal opinion is that the dielectric function does not need to be
provided with high accuracy.  Josh Kas may be able to make a more qualified
statement.

Like Bruce, I would be delighted to see a comprehensive study done.  It's
certainly on our minds and if anyone else has plans in this direction, I'm
sure we would be glad to support the effort.

Finally ...  Reading the referenced thread, I feel the need to clarify a
few things about the FEFF group...  We care a lot about our users and in
particular about this community.  It's a priority to make our codes useful
to this community as well as the wider FEFF community.  Personally I spend
loads of time responding to questions, testing other people's input files,
implementing requests, teaching, ... and wishing I had more time to
implement all the remaining things I would like to provide! -- just like
Matt or Bruce.  I invite everyone to contact me with any FEFF requests that
would benefit users, or to include me in ongoing developments.  And to end
on a cheerful note, I can happily report that FEFF8 for ifeffit EXAFS
analysis is ready to be given out!

Cheers and a late happy new year to everyone,

Kevin Jorissen

On Fri, Jan 10, 2014 at 8:13 AM, Bruce Ravel <bravel at bnl.gov> wrote:

> Hi Bao,
>
> This posting and its conversation thread is relevant to your question:
>
>
> http://www.mail-archive.com/ifeffit@millenia.cars.aps.anl.
> gov/msg03810.html
>
> The one thing that has changed since then is that progress has been
> made on making a version of feff8 with its XANES functionality
> stripped out and which can be redistributed.
>
> One thing that has not changed is that its integration into Artemis is
> very incomplete.  Following the instructions in my first response to
> that post may work for you with feff9.6.4.  Or maybe not.  I have no
> idea.
>
> Another thing that has not changed is my skepticism that feffN (where
> N>6) offers a substantial improvement for EXAFS data analysis.  As I
> said in that conversation, it may, but no one has demonstrated it tomy
> satistfaction.  Multi-pole self-energies are likely to represent a
> significant improvement in the EXAFS, but again, that systematic study
> has not been done.
>
> B
>
> PS: FWIW, getting feff8-for-EXAFS ready for use is something that
> neither Matt nor I have found much time for.  A volunteer would be
> very welcome.
>
>
>
>
> On 01/10/2014 11:00 AM, Bao Nguyen wrote:
>
>> Dear all,
>>
>> I’m new and have a daff question which must have been asked before:
>>
>> Can I refer Artemis to FEFF9.6.4, which I have, rather than the
>> standard-issued FEFF6 for more streamlined structural refinement?
>>
>> Many thanks!
>>
>> Bao Nguyen
>>
>> Tenure-track Research Fellow
>> School of Chemistry
>>
>> University of Leeds
>>
>> Woodhouse Lane
>>
>> Leeds, UK
>>
>> Tel: +44 (0)1133430109
>>
>>
>>
>> _______________________________________________
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>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>>
>
> --
>  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
>
>  Homepage:    http://xafs.org/BruceRavel
>  Software:    https://github.com/bruceravel
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