First‐Principle Analysis of the Structural, Elastic, Electronic, and Optical Properties of Novel AHgF ₃ (A = K and Fr) Perovskite

The fundamental physical properties of AHgF 3 (A = K and Fr) halide perovskites were studied in detail in this work, aiming to understand their basic physical properties and evaluate their potential to be used in optoelectronics. The crystallized KHgF 3 and FrHgF 3 were identified to contain compact and well‐ordered crystal geometries with values of 4.588 and 4.692 Å, respectively. The calculated formation enthalpy of –3.389 and –3.337 eV/atom shows that the structure is highly thermodynamically stable, and the tolerance factor value of 0.861 and 0.942 indicate that the structure is structurally feasible in the perovskite architecture. Poisson ratios of 0.385 and 0.350 were obtained by elastic analysis, and this proves their ductile nature and mechanical flexibility. Metallic‐like electronic response, mechanical ductility, and structural stability are all signs pointing to good charge transport and photon interaction characteristics. The moderate gaps between the bands and powerful Hg‐F covalent‐ionic bonding character of AHgF 3 compounds make them potential targets of applications in infrared to visible optoelectronic and energy conversion. These results all point to the fact that both KHgF 3 and FrHgF 3 have the structural strength and tunable electronic properties needed to serve in the applications of advanced functional materials and device engineering.