Self-energy correction to unrestricted Hartree-Fock solutions of lattice models for3dtransition-metal oxides

In order to explain the excitation properties of $3d$ transition-metal oxides in a unified framework, we have performed second-order perturbation calculations of the self-energy corrections around the unrestricted Hartree-Fock solution of lattice models using the electronic-structure parameters deduced from photoemission spectroscopy. The self-energy modifies the magnitude of the band gap and causes substantial spectral weight transfer over a wide energy range both in insulating and metallic compounds of the Mott-Hubbard type as well as of the charge-transfer type, resulting in an improved agreement between theory and experiment.