Theoretical study of structural and electronic properties of 2H-phase transition metal dichalcogenides

Computational physics and chemistry are called to play a very important role in the development of new technologies based on two-dimensional (2D) materials, reducing drastically the number of trial and error experiments needed to obtain meaningful advances in the field. Here, we present a thorough theoretical study of the structural and electronic properties of the single-layer, double-layer, and bulk transition metal dichalcogenides MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2 in the 2H phase, for which only partial experimental information is available. We show that the properties of these systems depend strongly on the density functional theory approach used in the calculations and that inclusion of weak dispersion forces is mandatory for a correct reproduction of the existing experimental data. By using the most accurate functionals, we predict interlayer separations, direct and indirect band gaps, and spin-orbit splittings in those systems for which there is no experimental information available. We also discuss the variation of these properties with the specific chalcogen and transition metal atom.