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. [Formula: see text]S 2 ([Formula: see text], 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 TaS 2 with GGA and HSE06 are [Formula: see text][Formula: see text]Å and [Formula: see text][Formula: see text]Å and [Formula: see text][Formula: see text]Å and [Formula: see text][Formula: see text]Å, respectively, while for TiS 2 these parameters are found as [Formula: see text][Formula: see text]Å and [Formula: see text][Formula: see text]Å. 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 1.9[Formula: see text]eV (PBE-GGA) and 2.05[Formula: see text]eV (HSE06) for TaS 2 and 0.09[Formula: see text]eV (PBE-GGA) and 0.13[Formula: see text]eV (HSE06) for TiS 2 . The mechanical study of these compounds also has been anticipated using Voigt–Reuss–Hill approximation under the pressure range 0–30[Formula: see text]GPa 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 TiS 2 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.