Nature of the hole states in Li-doped NiO

We have performed density functional calculations on Li0.125Ni0.875O using both the HSE06 hybrid functional and the density functional theory (DFT) $+$ U method. Contrary to previous calculations, both methods show that the system is better described with the hole localized on the nickel ion (which is thus formally Ni³⁺) rather than in the oxygen valence band. We discuss the experimental results in the light of this finding and show that it is consistent with the available data.