First principles calculations of structural, electronic and optical properties MoX2 (X = S, Se) metal dichalcogenides and their nano-layers

Abstract

Based on ab initio calculations, we have studied structural, electronic and optical properties of MoX2(X = S, Se) metal dichalcogenides and their nano-layers (NLs) according to the density functional theory using Wien2k code. The generalized gradient approximation (GGA) and GGA Engel-vosko are adopted to perform the exchange-correlation calculations. The equilibrium lattice parameters of MoS2 and MoSe2 compounds are calculated. The mechanical stability of these compounds is proved using Born condition. Moreover, the ductility and brittleness of MoX2 compounds are studied. The topological phase of MoS2 and MoSe2 bulks and their NLs is studied utilizing band order, Z2 invariant and surface density of states. The optical properties of MoX2 bulks and NLs are studied. The Penn model is satisfied for both MoS2 and MoSe2 compounds by studying their real part of static dielectric function. The increase of the thickness of these NLs leads to the changes in the absorption, reflectivity and energy loss function of these NLs in some specific energy ranges.