Structural and electronic properties of bulk and ultrathin layers of V 2 O 5 and MoO 3

The structural and electronic properties of bulk and ultrathin films of V 2 O 5 and MoO 3 layered oxides have been studied with first-principles density functional theory calculations including Van der Waals dispersion corrections. The U parameter in the DFT + U approach has been determined in order to properly reproduce geometry, band-gap, macroscopic dielectric constant, and formation enthalpies of the two materials. The mono-, and multi-layers are cleaved along the 〈0 0 1〉 and 〈0 1 0〉 stable crystallographic orientations for V 2 O 5 and MoO 3 , respectively. Three layers are needed in order to recover bulk-like properties of V 2 O 5 and MoO 3 . Spin-orbit effects have been incorporated in our simulations, and they result in marginal effects (∼20–30 meV) on the electronic band-gap of V 2 O 5 and a more pronounced (∼200 meV) effect on the band gap of bulk MoO 3 . We also discuss the importance of including local field effects for the reproduction of the anisotropy of the dielectric constant, which reflects the crystal structure of these materials