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

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-t 2g band decomposes in the trigonal symmetry into two bands, a 1g and e π. The a 1g band consists of orbitals connecting pairs of c-axis neighbouring atoms, while the e π 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 a 1g band from molecular (delocalized) to atomic (localized). The localization of the a 1g electrons causes through the atomic exchange interaction also the localization of the e π electrons, and this localization creates a gap in the e π 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.