Energy Bands of Metallic VO2

Abstract

At 68 °C, V${\mathrm{O}}_2$ undergoes a phase transition from a semiconductor with monoclinic structure to a rather poor metal with the rutile structure. We have performed a modified-augmented-plane-wave (APW) calculation for the metal phase, using a semiempirical potential chosen to give agreement with the experimentally determined energy difference between the top of the ${\mathrm{O}}_{2p}$ band and the Fermi surface. A tight-binding parametrized linear-combination-of-atomic-orbitals calculation was fitted to the three points in the Brillouin zone where APW energy levels were calculated, and the resultant energy bands and density of states are presented. Our results indicate that the poor conductivity is due to the flatness of the lower $d$ bands (and perhaps correlation effects) and not to any semimetallic nature of the energy bands. We also discuss the molecular-orbital picture of rutile Ti${\mathrm{O}}_2$ and V${\mathrm{O}}_2$.