[Ifeffit] FEFF calculation for two inequivalent absorbing sites

Eugenio Paris eugenio.paris at gmail.com
Thu Apr 9 05:01:34 CDT 2015

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!
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