Communicated by: FrancoisComprehensive DFT investigation of mechanical and electronic properties in Cs2AuMoX6 (X = Cl, Br) for advanced optoelectronic applications

This article investigated the mechanical, optoelectronic, and transport properties of the double perovskites Cs₂AuMoX₆ (X = Cl, Br) using density functional theory (DFT). We confirm that both Cs₂AuMoCl₆ and Cs₂AuMoBr₆ adopt a stable cubic crystal structure with slightly off unity tolerance factors (τ, 0.97 and 0.95). Negative formation and Gibbs free energies were used to validate their thermodynamic stability them for practical applications. Mechanical stability within a brittle nature and anisotropic behavior were observed in consideration of elastic properties. Electronic band structure calculations indicated Cs₂AuMoCl₆ has indirect band gaps of 1.4 eV while Cs₂AuMoBr₆ possesses 0.8 eV direct band gaps. Evaluation of these compounds suggests that these are appropriate band gaps for their application in photovoltaic and optoelectronics. The optical properties, including light absorption, polarization, and refractive index, exhibited strong absorption in the visible region, which renders these materials good candidates for photovoltaic applications. Calculations based on the BoltzTraP code predictions suggest modest thermoelectric figures of merit (ZT) of 0.73 and 0.72 for Cs₂AuMoCl₆ and Cs₂AuMoBr₆, respectively. These results demonstrate that Cs₂AuMoX₆ compounds may find applications in sustainable energy.