[Ifeffit] Question on XES in FEFF

FonsPaul paul-fons at aist.go.jp
Mon Mar 18 01:08:51 CDT 2019

I wrote a couple of days ago asking about XES calculations in FEFF9. But I didn't hear anything back so I am rephrasing the question with a little more detail. I am calculating XES for organic molecules and used the following input.

CONTROL 1 1 1 1 1 1


EXCHANGE 0 0 1.0

FMS 5.1

LDOS -30. 15. .1

PRINT 5 0 0 0 0 0


S02 1.0

SCF 4.5 0 30 .2 1

XES 8 0.05 0

The XES output is shown from what I understand in the xmu.dat file in the chi column, however plotting this data shows a curve that is not positive definite.  As I don’t think there is such a thing as negative emission, this probably means that my understanding is less than complete. The FEFF manual is also not very helpful on this issue and says nothing about the XES emission output. On a related question, the Feff9 docs (http://monalisa.phys.washington.edu/feff/Docs/feff9/feff90/feff90_users_guide.pdf) specify that the XES card has the following options:

XES emin emax estep
But the examples that come with JFEFF seem to show options that don’t make sense with this definition:

BN crystal:  XES -20 20 0.2
Cu: XES 8 0.07 0.0
GeCl4 (molecule):  XES 8 0.05 0.0

It is hard to understand how an emax value of 0.05 or 0.07 makes any sense. Does anyone know that the correct definitions are? Perhaps the documentation should be updated as well.

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