Licentiate seminar: Calculating X-ray absorption spectra for strongly correlated systems

The physics of correlated electron systems is highly complex and fascinating. A brilliant way to investigate these systems is found in X-ray absorption spectroscopy as many important properties can be extracted. For a deeper understanding of the interactions of electrons in solids, computational work is absolutely necessary, because one can test which theories hold true and which are false. In this work, a theoretical way of calculating X-ray absorption spectra with as few free parameters as possible will be introduced. Here, we go over the basics of density functional theory, dynamical mean field theory and multiple ligand field theory, which are combined in our model to calculate X-ray absorption spectra accurately. In the included paper, the theory is applied to the ferrites magnetite (Fe3O4), cobalt ferrite (CoFe2O4) and nickel ferrite (NiFe2O4).