Hi Anubhav,

> I'm trying to compare my experimental EXAFS data for a molten salt (NaF-ZrF4) sample (extracted through Athena), with EXAFS obtained through running FEFF iteratively on multiple atomic configuration files obtained through MD to get an average EXAFS out. This has been performed before by Pauvert et al. (https://doi.org/10.1021/jp203137h) for a similar salt as well as others for different materials.

> In our comparison, there seems to be a phase shift in MD EXAFS (to higher k) compared to experimental EXAFS and I would like to know if that's normal. I've read that there is an energy shift when we use FEFF and this might be affecting the MD EXAFS here but all the comparisons I've come across in literature overlay quite well...

I would say that “a phase shift (to higher k)” is not very clear.  A constant shift in k would not be normal.    A shift in the position of E0 (energy origin, where k=0) would be common – and there certainly can be differences in where an experimentalist selects E0 and where a FEFF calculation might but that value. OTOH, a shift in atomic distance would give a change in frequency.

We don’t typically analyze EXAFS by examining whether there are chi(k) shifts.  We model the data, which includes all those effects. I hope that helps.  If not, maybe you can give more details of what you are doing and what you see.