Influence of superexchange on Ni 2px-ray-absorption spectroscopy in NiO

In this paper we present a study of the effects of superexchange on the isotropic Ni 2p x-ray-absorption spectrum of NiO. The exchange interactions are included by performing model calculations on a cluster with two nickel atoms. It is shown that the spectra are sensitive to the nearest-neighbor exchange interactions and that the effect is larger than that obtained from a molecular-field approximation. We will also show that the first moment of the spectrum is proportional to 〈Sᵢ{·}Sⱼ〉.