[Ifeffit] Peak assignment and ionization potential with FEFF

Bruce Ravel bravel at bnl.gov
Fri Sep 13 15:10:17 CDT 2013

On 09/13/2013 03:25 PM, Ross Devol wrote:

> Does anyone know whether FEFF can be used to assign peaks? In other
> words, is there a way to tell which peaks in a calcite O K-edge
> spectrum are due to CO bonds and which to CaO bonds?  Also, does
> FEFF calculate the ionization potential and if so, where does it
> output this?

Feff is a real-space multiple-scattering code.  From the RSMS, your
question may not make a lot of sense.  The XAS spectrum is a measure
of how the photoelectron interacts with its surroundings.  In general,
peaks in the spectrum have something to do with all of the surroundings.

One way to get a handle, in some sense, on your question is to run
Feff with successively larger values of the FMS parameter.  That is,
see what features appear or change in the calculation as you increase
the radius of the cluster considered in the FMS calculation.

Also of interest will be the partial densities of state as a function
of cluster size.  That gives some hints of how Feff sees bonding in
your cluster.


  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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