Correlation effects in the electronic structure and photoemission spectra of mixed-valence cerium compounds

The electronic ground states and core-hole and valence-hole excited states of so-called tetravalent and mixed-valence Ce compounds are studied taking into account strong correlations among 4f electrons. By an analysis of the core-level photoemission satellites, CeO2, which has been thought to be tetravalent, is identified as a mixed-valence system with approx.0.6 4f electron, where the magnetic moment of the 4f1 configuration is quenched via singlet coupling between the 4f electron and the O 2p hole. 4f-derived satellite features in the resonant photoemission spectrum of CeO2 are calculated, which qualitatively explain resonant photoemission spectra of tetravalent Ce intermetallic compounds. The core-level and 4f-derived photoemission spectra of mixed-valence CeN are also studied by considering only the 4f-electron--N 2p-hole coupling as in CeO2 and neglecting the 4f-5d mixing. It is also suggested that for the α phase of Ce metal the absence of a localized magnetic moment, volume collapse, and a 4f0 signal in the core-level photoemission spectra are explained by this type of configuration-mixing description