[Ifeffit] Cumulant expansion fittings

[Patrick Kluth]

Hi Matt,

>Of course, XAFS *is* a one-dimensional probe, not a three-dimensional one.
>At least ignoring for the moment the angular dependence of multiple
>scattering, XAFS is sensitive to g(r) only.  Sadly, this is sometimes
>forgotten in the literature, and one sees attempts to distinguish
>"sigma^2_perpendicular" and "sigma^2_parallel", which is a good sign of a
>paper that is complete nonsense.
I don`t agree with you in this point. To my understanding, because 
EXAFS is a one-dimensional probe and it measures the average over 
instantaneous inter-atomic distances, it is only sensitive to the 
motion relative to each other along the bond-direction - and thus 
measures sigma^2_parallel. Combined with XRD which measures the the 
atomic motion averaged over all directions one can then extract a 
"sigma^2_perpendicular". If we are talking about the same literature 
this point is well elaborated in there and I don`t think it is 
nonsense. Please correct me if I am wrong.

Cheers,
Patrick

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Dr. Patrick Kluth
Fellow, ARC Australian Research Fellow
Department of Electronic Materials Engineering
Research School of Physics and Engineering
The Australian National University
Canberra, ACT 0200
AUSTRALIA

Phone: +61 2 6125 0358
Fax: +61 2 6125 0511
Mobile: +61 408 66 31 04
Email: patrick.kluth at anu.edu.au
http://www.rsphysse.anu.edu.au/eme
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