The energy diagram of NiO within an LCAO-LSDA+U approach

The itinerant LCAO picture based on localized atomic-like orbitals has been used to study the electronic ground state of NiO. The U-corrected local spin-density approximation (LSDA+U) yields energy-dispersion curves which show satisfactory agreement with the angular photoemission measurements. As a result the d states appear as narrow and well identified bands located above the 2p oxygen bands. The on-site Coulomb energy U increases the 2p character within the upper d valence band but not to the extent that NiO can be considered as a charge-transfer insulator.