A DFT+U study of the effect of transition metal replacements on optoelectronic and elastic properties of TmCu3S4 (Tm = V, Ta, Nb)

Abstract

One of the main goals of researchers is to develop renewable, ecologic and efficient energy sources to meet energy needs in the near future. In this context, chalcogenide materials are the most promising candidates for the production of clean energy from solar radiations using a new generation of technologically advanced solar cells. In this paper, we use first-principles GGA+U calculations to study the optoelectronic and elastic properties of TmCu3S4 (Tm = V, Ta, Nb) in terms of their potential applications in optoelectronic devices. Our calculations show that VCu3S4 is a half-metallic compound, showing metallic properties in the spin up channel and semiconducting properties in the spin down channel. On the other hand, NbCu3S4 and TaCu3S4 are semiconductors. VCu3S4 has a direct bandgap in spin down channel as the CBM (conduction band minima) and VBM (valence band maxima) occur at the same point Γ. However, NbCu3Se4 and TaCu3Se4 are indirect bandgap semiconductors. The values of bandgaps for above-mentioned materials are increased by replacing Nb with Ta and V. The prospect of TmCu3S4 (Tm = V, Ta, Nb) for optoelectronic applications is demonstrated by detailed examination of optical parameters. This study reveals that TmCu3S4 (Tm = V, Ta, Nb) are week reflectors of incoming photons, and a maximum of 50% reflection of incoming photo radiations is depicted by these materials in the upper UV region for both spins. In the elastic properties, the values of Zener anisotropy factor A indicate that the cubic materials mentioned above are anisotropic and have covalent bonds. The material will be brittle if value of the Pugh’s ratio (B/G) is less than 1.75, otherwise it will be substantially plastic. In this study, values of Pugh’s ratio (B/G) TmCu3S4 (Tm = V, Ta, Nb) are below 1.75. Therefore, these cubic chalcogenides are fragile.