Free electronic states of UO2: Analysis of x-ray absorption by total multiple scattering

The experimentally observed x-ray absorption spectrum of oxygen in UO₂ is analyzed theoretically. The experimental absorption spectrum of oxygen is shown to agree well with details of the density of free p states of oxygen in the conduction band. It is found that a minimum cluster of atoms surrounding an absorbing oxygen ion required to reproduce all the details of the fine structure of the density of states at the bottom of the conduction band is of the order of 40 atoms. An analysis of the densities of the electronic states reveals the existence of hybridization of free p states of oxygen with s states of uranium in the conduction band of UO₂, as well as the exclusion of p states of oxygen by d states of uranium beyond the confines of the energy interval where they are localized. Fiz. Tverd. Tela (St. Petersburg) 41, 1385–1388 (August 1999)