[Ifeffit] polarization in Artemis

Bruce Ravel bravel at bnl.gov
Sun May 24 16:37:52 CDT 2015

On 05/24/2015 05:03 PM, Matt Newville wrote:
> You mean Artemis wasn't creating a POLARIZATION card?   But one can just
> go in and add that the the Feff.inp anyway, no?   The feff.inp file is
> editable before running Feff with Artemis all the time, right?  That
> should be independent of pathfinder.  Or do you mean something else?

I mean something else.  The pathfinder did not consider polarization AND 
when Artemis ran the genfmt part of feff, the polarization card was not 
passed along.  So, regardless of whether you edit the feff.inp window to 
included a POLARIZATION card, that information was not being passed to 
feff when the feffNNNN.dat file was generated.  There's no convenient 
way to intervene in that step.

It's been years, with not much complaint, so I kind of forgot about it. 
  My apologies to George Strbinsky -- I should have fixed it when he 
asked me about this a couple years ago.

All of that will be fixed soon, with the caveat that ellipticity will 
not yet be supported by Artemis.  (So the "polarization in the plane" 
trick won't work in Artemis.  Again, this is an Artemis shortcoming, not 
a Feff shortcoming.)

> I understand VPaths, I think. But I meant simply "sum these paths
> applying the current parameters, without fitting".      That used to be
> very, very simple and I always find it useful and instructive for
> exploring the contributions from different paths.  Now it seems I have
> to set all values to "set", then change them to "guess" to really do a
> fit.   Am I missing something?

Well, I suppose it is possible that things aren't working as intended, 
but the intent is that you could make a VPath out of /all/ the paths 
(i.e. select "Mark all" from the Mark menu, then select "Make VPath" 
from the actions menu, then plot in k, R, or q). The intent also is that 
the current values for all parameters will be used when the plot is 
made.  If no fit has been performed, the initial values will be used. 
It should not be necessary to change all guesses to sets just to make 
that plot.

I suppose that could be streamlined...


  Bruce Ravel  ------------------------------------ bravel at bnl.gov

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 535A
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/

More information about the Ifeffit mailing list