Geometrical-, Electronic- and Optical Properties of Vanadium Dioxide: A Theoretical Perspective from Meta-GGA SCAN

Meta-GGA (SCAN, and SCAN-rVV10) density functionals were used to determine the lattice constants, cell-volume and -density, phase-stability, bandgaps and dielectric functions of experimentally recognized non-magnetic VO2 in the monoclinic (M1) and rutile (R) phases. Our results suggest that these functionals can adequately predict the most important geometrical and optoelectronic properties of VO2 that are not only in excellent agreement with experiment but also better than those reported using GGA and GGA+U. In specific, we have shown that SCAN-rVV10 correctly predicts the preferential energy stability of low-temperature monoclinic phase over the high-temperature rutile phase of VO2, in agreement with the experimental latent heat of phase transition between the two phases (44.45 meV). A bandgap of approximately 0.58 eV for VO2(M1) was obtained with the two meta-GGA functionals, which is also consistent with experiment (0.6-0.7 eV). Although the meta-GGA predicted absorption peaks of the imaginary part of the dielectric function in the near infrared region has displayed reasonable match with experiment, it overestimated the absorption peaks in the visible region. Our results suggest that the degree of exchange and electron-electron correlation incorporated in meta-GGA SCAN, and its van der Waals analogue, SCAN-rVV10, is appropriate in reproducing the experimentally observed V-V chain features that are linked with the insulator-to-metal phase transition. The optical dielectric features computed with GGA and meta-GGA were compared with many-body theory (at the G(0)W(0) (RPA) and G(0)W(0)-BSE level(s)) and discussed.