Exploring Stability, Mechanical, Optoelectronic, and Thermoelectric Characteristics of Halide Double Perovskites Li₂YAuX₆ (X = Br or I) for Energy Harvesting: A DFT and AIMD Approach

Herein, the structural features, mechanical stability, electronic response, optical properties, and thermoelectric aspects of Li 2 YAuX 6 (X = Br or I) are examined via first‐principles computations. The Born‐Huang criterion, formation energy, and tolerance factor ensure the mechanical, thermal, and structural stabilities. Several elastic characteristics have been obtained, including elastic constants, moduli, ductility, wave velocities, Debye temperature, and melting points. The data on elastic features indicate that Li 2 YAuBr 6 and Li 2 YAuI 6 possess ductility and sufficient flexibility to be employed in flexible solar devices. Moreover, the estimated band gap values for Li 2 YAuBr 6 and Li 2 YAuI 6 are 2.65 and 2.15 eV, respectively. The obtained band structures demonstrate the semiconducting nature with indirect band gaps. The density of states has been ascertained to determine the contributing states in electronic transitions. The optical features have been calculated to evaluate the response of both materials to incoming light photons. Li 2 YAuBr 6 is effective at photon absorption over the ultraviolet (UV) spectrum, whereas Li 2 YAuI 6 demonstrates visible and UV light absorption, making them suitable for photovoltaics. Thermoelectric aspects have been calculated to analyze the performance of materials for deployment in wasted heat conversion technologies. The minimum heat conduction and increased power factor lead to considerable ZT values of 0.79 and 0.81. These findings suggest that these materials have great promise for application in photovoltaic and thermoelectric systems.