Unveiling the mechanical, structural, thermoelectric, and optoelectronic potential of K2NaGaBr6 and K2RbTlBr6 double perovskites for sustainable technologies

Double perovskite halide's remarkable physical qualities and ease of synthesis have drawn much interest in the past few years. To analyze the structural and thermodynamic stability, elastic traits, optical, and thermoelectric analysis of the double perovskites K 2 NaGaBr 6 and K 2 RbTlBr 6 , FP-LAPW technique is employed in current work. Exchange correlation effects are treated with PBE-GGA and TB-mBJ approximations. Thermodynamic stability of structures is ensured with computed phonon curves and negative formation energies. Goldsmith tolerance factor and octahedral tilting justify the cubic phase of both perovskites. Mechanical attributes justify Born's stability criteria and double perovskites' anisotropic and ductile nature. The semiconducting nature is confirmed by electronic band structures with direct bandgap of 1.43 eV and 3 eV for K 2 NaGaBr 6 and 1.48 eV and 2.51 eV for K 2 TlRbBr 6 with PBE-GGA and TB-mBJ, respectively. Optical properties for K 2 NaGaBr 6 and K 2 RbTlBr 6 reveal significant absorption of electromagnetic waves in visible and UV regions. Furthermore, thermoelectric response for both double perovskites is computed using BoltzTraP code, which reveals their significant abilities for usage in thermoelectricity and renewable energy applications.