The effect of ligand correlations on the one-electron removal valence band of NiO

Based on cluster calculations performed by applying the Anderson hamiltonian in the impurity limit, the effect of oxygen 2p hole correlation on the one-electron removal valence band pf NiO is discussed in connection with an analysis of the nature of the lowest ionisation state. It is shown that the low-spin 2Eg configuration in the NiO 3d removal spectrum attains the lowest binding energy on the assumption that double charge-transfer screening from 3d9L2 configurations in the final state is favoured and the related correlations between ligand holes are negligible.