First-principles studies of the electronic and structural properties of vanadium dioxide and characterization of VO₂(011) surfaces

Vanadium dioxide is used in various applications such as field-effect transistors or ultra-fast optoelectronic switches. Standard GGA functionals (PBE, PBESol) fail to describe the band gap of 0.6 - 0.7 eV and predict the monoclinic phase to be metallic. Another contradiction to experiments is that the rutile phase is calculated to be 65 - 95 meV / f.u. more stable than the monoclinic (M1) phase. Using the meta-GGA+U (SCAN) functional with the treatment of van der Waals interactions (rVV 10) or hybrid functional (PBE + 7% HF exchange) calculations, we obtained the band gap of 0.65 eV (hybrid) and 0.73 eV (meta-GGA) which is in a good agreement with optical photoemission experiments. Furthermore, hybrid functional calculations improve the description of the band width in the rutile phase. However, both functionals still predict the rutile phase to be 406 meV / f.u. (meta-GGA) and 65 meV / f.u. (hybrid) more stable than monoclinic (M1) phase.
We will also discuss reconstructions of the rutile (011) surface and compare them with recent STM experiments performed on metallic VO₂ (011) single crystals.