Ab initio investigation of the optical properties of layered MoSxSe(2-x) (0 ≤ x ≤ 2): By GGA and mBJ approaches

Based on the density functional theory (DFT) and using the generalized gradient approximation (GGA) and GGA-mBJ approximations, the electronic and optical properties of the bulk and mono-layer Molybdenum sulphoselenide MoSxSe(2-x) (0 <= x <= 2) are calculated. In both bulk and mono-layer cases, the energy gap decreases by increasing the density of the Se atom, so that the reduction in the mono-layer case is more observable than the bulk case. Also, the variation of the exchange-correlation (XC) potential has the maximum and minimum effects on the bulk MoS2 and the mono-layer MoSe2 cases, respectively. The static dielectric function of MoS2 in the epsilon(1)(omega) as well as its optical conductivity is less than the other two compounds. In the mono-layer case along x-direction, the first response to the incident photon belongs to MoS2 in the infrared region, while the other two compounds respond in the edge of the visible area. The intensity of the MoSSe response, unlike its bulk case, is less than the other compounds. Along z-direction, the first response is observed in the visible area. The remarkable point is that the optical stability in the bulk case is more than that in the mono-layer case.