X-RAY-ABSORPTION OF TRANSITION-METAL OXIDES - AN OVERVIEW OF THE THEORETICAL APPROACHES

A short overview is given of the different approaches to interpreting X-ray absorption spectroscopy (XAS), and particularly their relation to electronic structure models. The electronic structure models which incorporate many-electron effects, such as GW calculations, the Hubbard model and self-interaction corrected local density approximation (LDA) calculations, are outlined. Special attention is given to the use of Hubbard model for core level spectroscopies. Within this background two extreme models for interpreting X-ray absorption spectra are discussed in detail: the ligand field multiplet model to interpret metal 2p-XAS spectra and LDA calculations to interpret oxygen 1s-XAS spectra. Finally the open problem of possible final state effects on model hamiltonians is outlined.