Orbital occupation, local spin, and exchange interactions in V2O3

A local-density-approximation (LDA) and LDA + U band structure study of var ious phases of V2O3 shows that the most prominent (spin-1/2) models used to describe the semiconductor-metal transition are not valid. We find that th e large on-site Coulomb and exchange interactions result in a total spin of 1 rather than 1/2 and especially an orbital occupation which largely remov es the orbital degeneracy. The calculated magnetic structure is consistent with experiment, again without the need for orbital ordering. These results : strongly suggest that the phase transition in V2O3 which is so often quot ed as the example Of a spin-1/2 Mott-Hubbard system have a different origin .