First-principles calculations were performed to investigate the pressure dependent structural, electronic, mechanical, optical, and thermal properties of ASiF 3 (A = Na, K, Rb) fluoroperovskites from 0 to 12 GPa using DFT within the GGA-PBE functional. Band-structure analysis shows that NaSiF 3 , KSiF 3 and RbSiF 3 are direct bandgap semiconductors at ambient pressure, with GGAPBE band gaps of 0.609, 0.805, and 0.918 eV, respectively. The bandgaps decrease strongly under compression, and additional GGA+U and HSE06 calculations confirm pressure-induced bandgap narrowing. Within HSE06, the bandgaps decreased from 1.198, 1.730, and 1.782 eV at 0 GPa to 0, 0.642, and 0.671 eV at 12 GPa for NaSiF 3 , KSiF 3 and RbSiF 3 , respectively. Lattice parameters and bond lengths reduce at higher pressures, confirming lattice compression while preserving the cubic crystal framework. Optical conductivity and absorption are improved with a red shift to lower photon energies under pressure, indicating a pressure tunable optical response. Mechanical analysis indicates anisotropic and ductile behavior, with KSiF 3 and RbSiF 3 showing better stability under compression than NaSiF 3 . Thermal analysis shows pressure dependent Debye temperature, melting temperature, and lattice thermal conductivity. These results indicate the possible relevance of lead-free ASiF 3 fluoroperovskites for pressure-tunable optoelectronic and ultraviolet photonic applications.
Mahmud et al. (Fri,) studied this question.