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.

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