A model for the metal-to-insulator transition in V2O3

Abstract

The metal-to-insulator transition in V2O3 is described by a model that is based on the electronic band structure of this material. The vanadium 3d-t2g band decomposes in the trigonal symmetry into two bands, a1g and eπ. The a1g band consists of orbitals connecting pairs of c-axis neighbouring atoms, while the eπ band consists of orbitals in the plane perpendicular to the c-axis. The change in distance between c-axis neighbours changes the nature of the a1g band from molecular (delocalized) to atomic (localized). The localization of the a1g electrons causes through the atomic exchange interaction also the localization of the eπ electrons, and this localization creates a gap in the eπ band which causes the material to become insulating. This model is treated in the Hartree-Fock approximation (the ‘Excitonic’ model) at zero and finite temperatures, and various aspects of the transition, such as changes in the c/a ratio, the creation of magnetic moments, changes in covalency, the effect of pressure and the order of the transition, are investigated.