Mechanical, thermal, electronic and optical properties of Cu3NbS4: an ab-initio study

In this work, mechanical, thermal, electronic and optical properties of Cu3NbS4 are evaluated by using density functional theory (DFT). The mechanical properties of Cu3NbS4 in the cubic phase are calculated by PBEsol approximation. By using calculated Young's modulus and shear modulus, with Poisson's ratio, conclude that the Cu3NbS4 structure is brittle material and also the 3D graphs of these parameters explained that the Cu3NbS4 behaves in a pseudo-symmetric manner. The calculated Debye temperature (theta(D)) for Cu3NbS4 is 429.2 K which allowed the use of the Debye-Gruneisen model to study the thermodynamic properties below this mention temperature. The amount of C-v and C-p of Cu3NbS4 at zero pressure and room temperature are studied and showed that these two curves cross each other, above 200 K. Furthermore, the electronic properties of Cu3NbS4 are studied and the results explain this structure has an indirect band gap in the zero temperature. The real part of the dielectric function and the static dielectric constant curves under different strain for Cu3NbS4 are investigated. The static dielectric constant decreases under tensile strain and increases under the compressive strain. The reflectivity under the different strains shows that the main peak shifted to higher energy (blue shift) under compressive strain and it shifted to lower energy (red shift) under tensile strain. Also, this compound shows strong optical absorption, with the absorption coefficient reaching 10(6) cm(-1) that it has potential applications in solar cell industries.