Electronic structure calculations for two-dimensional transition metal oxides

Abstract

Electronic states of oxides including 3d, 4d and 5d transition metals with metal ion d 1 configuration were calculated using the spin-polarized DV-Xα method. Artificial model clusters adopted were MO 6 octahedra, MO 5 pyramids and square planar MO 4 (M=transition metal). For the undistorted octahedron, d orbitals of the metal ion split into partially occupied levels t 2g and unoccupied levels e g. The degenerate orbitals t 2g, whose components are d xz , d yz and d xy , do not have a two-dimensional character. For the octahedron whose M-O bonds in the xy( ab)-plane are elongated, metal d xy and oxygen p π form two-dimensional half-filled states. In this case, the metal oxide probably becomes an insulator, and the p π contribution to the half-filled states increases as the atomic number becomes larger. Concerning the square planar, metal d z2 , oxygen p σ and metal s form the two-dimensional half-filled states. The energy separation between d and p orbitals is smaller compared to the octahedron.