Correlation assisted metal-insulator transition in the high temperature tetragonal rutile vanadium dioxide

Vanadium dioxide is a nonmagnetic metal in high temperature rutile phase and undergoes metal-insulator transition (MIT) upon the application of Coulomb interaction U = 5 eV. The insulating phase is ferromagnetic. By employing first principle electronic structure calculations implemented in the density functional theory, it has been found in the LDA approximations that d_xy, d_yz and d_x^2-y2 states are almost degenerate and responsible for non opening of a gap in the close vicinity of Fermi level (E_F). In the LDA+U approximations, strong Coulomb interactions play crucial role in the MIT of VO₂ in the high temperature rutile phase. Application of Coulomb interactions increases orbital polarizations and hence static electron correlations for which d_x^2-y2 state becomes completely occupied and shifted below E_F whereas, d_yz and d_xz states become empty and shifted above E_F resulting opening of a band gap near E_F. The hybridizations between occupied V - 3d_x^2-y2 and O-2p orbitals are responsible for observed ferromagnetic behavior of VO₂ in the insulating phase. (author)