Energy Bands of Semiconducting VO2

Abstract

For $T>\mathrm{}{T}_t\simeq 68$ ° C, V${\mathrm{O}}_2$ is a metal with the rutile structure. For $T<\mathrm{}{T}_t$, V${\mathrm{O}}_2$ is a semiconductor with a monoclinic structure. We have found semiconducting energy bands for the low-temperature structure from a parametrized tight-binding linear-combination-of-atomic-orbitals calculation. The semiconducting gap results not only from the reduced symmetry of the monoclinic phase but also from changes in the tight-binding parameters which result from changed interatomic distances. The joint density of states derived from our calculation is in very good agreement with experimental optical data. The success of this calculation shows that, given the crystal structure, the semiconducting band gap is completely understandable in terms of one-electron theory. A short Appendix on the group theory of this structure is included.