[Ifeffit] FEFF calculation for two inequivalent absorbing sites

Bruce Ravel bravel at bnl.gov
Thu Apr 9 15:04:35 CDT 2015

Regarding the "Aggregate" button, it is important to understand what 
that button is trying to do.  It is a tool that is very easy to misuse, 
or at least get confused by.

You should read this page from the manual:


and this article:


If it's what you're looking for, cool.


On 04/09/2015 06:01 AM, Eugenio Paris wrote:
> Hello everybody,
> I'm trying to make Co K-edge EXAFS fitting for the Co3O4 compound (*.cif
> file is attached). The nearest neighbour of Co is oxigen at about 1.93
> Angstrom distance.
> Cobalt sits in two inequivalent sites in the unit cell. When I perform
> the FEFF calculation in Artemis for either one or the other site i get
> the same path with Reff = 1.93 and degeneracy = 4.
> So i wonder what is the correct way to take account of the presence of
> both sites. At the beginning i was thinking to put 2*amp as S0^2
> parameter to take account for twice the coordination number.
> Then i tried to use the "Aggregate" option in Artemis. When I use this
> option i get exactly the same result, i.e. a SS path with Reff = 1.92
> and degeneracy = 4... I was expecting to get twice the degeneracy.. (the
> margin and beta parameters are set to default)
> My question is:
> Why do i get the same path list when I do use the "Aggregate" pathfinder
> and when I don't? What is wrong in my interpretation?
> Thank you in advance!
> Sincerely,
> Eugenio
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  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/
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