AbstAb-initio insights into the elastic, bonding, phonon, optoelectronic and thermophysical properties of SnTaS2

Abstract

SnTaS2 is a layered topological semimetal exhibiting type-II low transition temperature superconductivity. Except some charge transport, electronic and superconductivity related properties, a number of the physical properties including elastic, mechanical, bonding, phonon dispersion, acoustic, thermal, and optical properties of SnTaS2 have not been explored comprehensively till now. In this work we have investigated all these physical properties of SnTaS2 employing the density functional theory (DFT) based first-principles methodology. It has been found that SnTaS2 is a mechanically stable, elastically anisotropic compound exhibiting strongly layered features. The bond hardness and Vickers hardness have been calculated. The material under study is ductile, soft and highly machinable. The chemical bonding has mixed character with significant contribution coming from the ionic channel. Phonon dispersion curves testify dynamical stability. Electronic band structure calculations show simple metallic character in agreement with previous results. The Fermi surface consists of both electron-like and hole-like sheets with varying degrees of energy dispersion. The low energy (encompassing the visible part of the optical spectrum) refractive index of SnTaS2 is high. The reflectivity is fairly nonselective over a wide range of photon energy and the absorption coefficient is large in the mid ultraviolet region. The Debye temperature and thermal conductivity of SnTaS2 are found to be low. The electron-phonon coupling constant has been calculated. SnTaS2 possesses optical anisotropy with respect to the polarization direction of the incident electric field.