Study of the structural and electronic properties of three- and two-dimensional transition-metal dioxides using first-principles calculations

Abstract

The structural, electronic and magnetic properties of three- and two-dimensional transition-metal dioxides (VO2, CrO2, MoO2 and WO2) have been studied based on density functional theory. We found that the equilibrium structural parameters of monolayers change slightly with respect to the structural parameters of their counterparts in bulk, and that the cohesion energies calculated for dioxides in bulk and their corresponding monolayers are all positive and with the 5.0–7.0 eV/atom range. Additionally, the calculated formation energies of the bulk are greater than the energies of its receptive monolayer, indicating that the compounds in bulk are more stable than their corresponding monolayers, as expected. For the monolayers, the exfoliation energies obtained were 16.25, 18.69, 19.21 and 62.55 meV/A2 for VO2, CrO2, MoO2 and WO2 monolayers respectively. These values are close to the exfoliation energy of graphene (21 meV/A2), except for the WO2 monolayer and exfoliation energy values are not available theoretically nor experimentally. Finally, the study of the band structure and the density states shows that VO2 exhibits a magnetic metallic behavior both in bulk and in monolayer, reaching a magnetic moment of 0.22 μβ/atom which is produced by the hybridization and polarization between V-d and O-p. Meanwhile, the CrO2, MoO2 and WO2 materials have a non-magnetic semiconductor behavior both in bulk and in monolayer.