On the Neglect of Local Coulomb Interaction on Oxygens in Perovskites Described by the Multi-band $d-p$ Model

Abstract: On the example of TiO$_4$ layer (such as realized in Sr$_2$TiO$_4$) we study electronic structure of multi-band $d-p$ models describing transition metal perovskites. In agreement with the experiment, the studied system is predicted to be a robust nonmagnetic insulator. A realistic treatment of electronic structure requires one to introduce non-zero Coulomb local interactions at $2p$ oxygen orbitals. However, up till now majority of papers based upon multi-band models made an approximation of neglecting such interactions. We show that this simplification does not lead to serious problems in predictions of the electronic structure provided the Coulomb interactions at titanium ions and charge transfer gap are suitably renormalized (so they become entirely different with respect to the true microscopic $d-p$ model parameters).