Structural, mechanical, optoelectronic and thermoelectric properties of double perovskite compounds Cs2TeX6 (X = Br, I) for energy storage applications: First principles investigations

First principles calculations were performed to investigate the structural, mechanical, optoelectronic and thermoelectric properties of double perovskite Cs2TeX6 (X = Br, I) compounds in the cubic structure using the full potential linearized augmented plane wave method. The main results are founded as follows: (1) Calculations reveal the indirect band gap for the two materials; our results are in agreement with the available experimental and theoretical data. (2) The elastic constants Cij's indicate that the cubic phase is mechanically stable and reveal ductility behavior. (3) The real and imaginary parts of dielectric function for the cubic phases for both compounds demonstrate an optical band gap similar to the electronic one and a substantial absorption in the ultraviolet region of the spectrum in elevated energy level. (4) Thermoelectric properties are reported as a function of temperature ensuring a beneficial trend of these materials in energy storage applications.