Speaker
Description
Halide double perovskites (HDPs) have emerged as compelling candidates for next-generation optoelectronic applications owing to their tunable band gaps, structural versatility, and environmental compatibility. Despite the known advantages of fluoride-based HDPs, this subclass remains significantly understudied. In this work, we employ density functional theory (DFT), as implemented in Quantum ESPRESSO, to investigate the tunability of the structural, electronic, mechanical, and optical properties of the antimony-fluoride double perovskites X₂AgSbF₆ (X = K, Rb) under hydrostatic pressures ranging from 0 to 100 GPa. At ambient pressure, both compounds crystallize in the cubic Fm-3m space group and are confirmed to be structurally, thermodynamically, and mechanically stable, exhibiting ductile and anisotropic behavior. They are indirect band-gap semiconductors with band gaps of 0.29–2.02 eV and strong visible-to-UV optical absorption coefficients of ~10⁵ cm⁻¹. Under applied hydrostatic pressure, the electronic band structure evolves significantly: the band gap narrows progressively with increasing pressure, indicating a pressure-induced semiconductor-to-metal transition at sufficiently high pressures. The elastic constants increase substantially with pressure, reflecting enhanced stiffness. The optical response is similarly pressure-sensitive, with absorption edges and dielectric features shifting toward lower energies under compression, broadening the potential absorption window. These results demonstrate that hydrostatic pressure is an effective tuning parameter for engineering the optoelectronic and mechanical properties of X₂AgSbF₆ (X = K, Rb), establishing these lead-free fluoride double perovskites as strong candidates for pressure-tunable optoelectronic device applications.
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