[Ifeffit] Question related to an example of EXAFS fitting using Larch

[Andy Zhang]

Dear all,

I am learning Larch and read the manual of Larch online. In the "13.8.10.
Example 3: Fit 3 datasets with 1 Path" of the webpage
https://xraypy.github.io/xraylarch/xafs_feffit.html#example-3-fit-3-datasets-with-1-path-each,
it shows an example that fitting Cu at different temperatures.
Einstein model was used to simulate the sigma2, as shown in the figure
below.

[image: image.png]

However, in some papers (eg. Radiation Physicsand Chemistry137 (2017)
93–98) that model EXAFS at elevated temperatures, they separates the total
sigma2 to static and thermo components (Sigma^2 = Sigma_static^2 +
Sigma_thermo^2), which is different from the above Larch example.

I am a little confused about the utilization of Einstein model. I wonder if
the Sigma2 obtained by Einstein model can reflect the total sigma2 or can
only reflect the thermo part.

Many thanks for your help!

Best regards,
Harry
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