[Ifeffit] EXAFS signal from dopant atoms

[Eugenio Paris]

Dear all,

I have a very general question about EXAFS analysis.
Let's take as example a binary system AB in which i am substituting the
atom B with another atom C so that we have AB(1-x)C(x). Let us imagine that
we know the structure of binaries AB and AC with Rab and Rac atomic
distances and we know that in AB(1-x)C(x) the substitutional site will be
100% the B-site.

If I measure the EXAFS spectrum of atom C as a function of "x" what can I
expect for the EXAFS oscillations? My idea is that when "x" is very small
the EXAFS will be highly noisy and damped, while as "x" increases the
oscillations will become more evident above the noise level.

How to model this situation to get information on C-A bond? In Athena I can
start with the .cif file of AC structure with full occupancy and obtain the
distance and the DWF for the A-C bond but.. how to treat the
signal-to-noise ratio? I mean, as "x" decreases I think there must be a
leaking out of the EXAFS signal, should this effect be introduced in S0^2?
Or can it affect the effective number of neighbors?

Hope I explained myself,
thank you!

Eugenio Paris
PhD student, University of Rome (Italy)
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