Mixed valence compounds - XAS spectra

Dear all,

I am a PhD student trying to simulate XAS spectra of a mixed valence compound. The nominal electron count according to the stochiometry is 7.5, while DFT calculations show that the number of electrons on (one of) the ions is closer to 8.3. However, the StartRestrictions field in the Eigensystem function allows only for an integer number of electrons. I could not find any literature specifying how to tackle this problem.

Thus I am unsure about what the correct method for obtaining the spectra is:

i) Performing two calculations with 7 and 8 electrons as an initial filling and summing the spectra in such a way that the groundstate occupation agrees with the DFT results. In this case, do I take the Delta to be the same in both calculations?

ii) Performing a calculation with 8 electrons (or 7?) initial filling and tune the charge transfer energy such that the occupation is close to the DFT result

iii) Something else entirely

Any hint in the right direction is much appreciated!

Thanks and best regards

Manuel Knauft