The nature of valence band holes in pure and Fe-doped NiO: an ab initio Hartree-Fock study

First principles periodic Hartree-Fock calculations of the first ionised state of Fe0.125Ni0.875 are reported from which the Mulliken populations, charge and spin distributions and atom projected densities of valence band states provide direct evidence of Fe(3d) holes in complete agreement with recent conductivity measurements on materials with approximately the same composition. This is in marked contrast to the self-trapped hole in NiO also reported here, and the bound hole in Li-doped NiO where both experiment and a recently reported calculation find holes of predominantly O(2p) character.