A First-Principles Study of the Nature of the Insulating Gap in VO2

Upon cooling past a critical temperature Tc = 340 K Vanadium dioxide (VO2) exhibits a metal-insulator transition (MIT) from a metallic rutile R to an insulating monoclinic M1 phase. Other insulating phases, a monoclinic M2 and triclinic T, have been identifed and are accessible via strain or doping. Despite decades of research, the nature of the VO2 MIT is still not fully understood. In this work we present ab-initio hybrid density functional theory (DFT) calculations on the insulating phases, compare the results to experimental measurements and discuss their implications on our understanding of the VO2 MIT. Recent measurements on M1 VO2 under high pressure found a transition to a metallic monoclinic state X at Pc = 34.3 GPa. Following this increased interest in the study of VO2 at high pressures, we will also present results of hybrid-DFT calculations on the M1 phase under increasing pressure. Our calculations predict that M1 may become metallic above ∼32 GPa, in good agreement with experiment