Fig. 1: Schematic single-electron removal spectra of NiIII oxides with a formal 3d7 filling.
From: Unusual double ligand holes as catalytic active sites in LiNiO2
a Δ < 0 and b Δ > 0 scenarios. Charge-transfer energy Δ: energy cost for electron transferring from the O 2p band to the Ni 3d band, and U: energy cost for electron transferring from the occupied 3d band to the unoccupied 3d band. The hybridization between Ni 3d and O 2p is neglected for simplicity. The Fermi level (EF) is shown as a vertical dash black line and the O 2p band is used as the energy reference considering the position of EF is arbitrary in the band gap.
