FIRST-PRINCIPLES SIMULATION: STUDY OF THE STRUCTURAL, ELECTRONIC, MECHANICAL AND OPTICAL PROPERTIES OF DISULFIDE XS2 (X=Ta, Ti) COMPOUNDS FOR OPTOELECTRONIC APPLICATIONS

First-principles simulation has been performed to investigate the structural, electronic and optical properties of two disulfide compounds, i.e. XS2 (X=Ta, Ti). The properties are examined through the density functional theory (DFT) with the implementation of Cambridge series total energy package (CASTEP) code. As regards, the structural and electronic analyses are done by Perdew–Burke–Ernzerhof-generalized gradient approximation (PBE-GGA) and hybrid Heyd–Scuseria–Ernzerhof (HSE06) functional and their results are compared herewith. The values of lattice parameters obtained through geometry optimization for TaS2 with GGA and HSE06 are a=b=3.27Å and c=12.89Å and a=b=3.31Å and c=12.09Å, respectively, while for TiS2 these parameters are found as a=b=3.39Å and c=5.69Å. These values are found in agreement with the experimental values. The electronic band structure, as well as density of states (DOS) of these structures, show their semiconducting nature with the direct bandgap of 1.9eV (PBE-GGA) and 2.05eV (HSE06) for TaS2 and 0.09eV (PBE-GGA) and 0.13eV (HSE06) for TiS2. The mechanical study of these compounds also has been anticipated using Voigt–Reuss–Hill approximation under the pressure range 0–30GPa to show their stability by calculating the elastic parameters, i.e. Young’s modulus, bulk and shear modulus, Poisson’s ratio, Pugh’s ratio and anisotropic factor. The analysis of optical properties divulges that TiS2 material possesses maximum absorptivity in the UV range of incident photon’s energy with minimum energy loss and decrease in reflectivity. Our comprehensive study about the considered compounds delineates them as potential candidates for technological applications in optoelectronic devices.