Band-structure effects in the core-level photoemission spectra of NiO

Calculation of Ni $2p$ photoelectron spectra for NiO has been performed within a picture which takes into full account the itinerant character of valence electrons and the localized many-body interaction between core and valence electrons. The results of an ab initio band-structure calculation are used as an input for the calculation of self-energy correction and spectral function according to a three-body scattering solution of a many-body Hamiltonian which includes the Coulomb repulsion between core and valence states. The calculated spectrum shows, in agreement with experimental data, a doubly peaked main line which can be attributed to two independent relaxation processes involving valence-band Ni d states of either pure or hybridized orbital character.