Unlocking Phase‐Dependent Physical Properties of BeLiF ₃ Fluoroperovskites for Solar Cell and Smart Window Applications

ABSTRACT Fluoroperovskites are crucial in materials research due to their exceptional optoelectronic properties and multifunctionality. Therefore, this study provides a comprehensive exploration of the physical properties of BeLiF 3 fluoroperovskite employing first‐principles computational methods based on density functional theory (DFT). Initially, two distinct α‐BeLiF 3 and β‐BeLiF 3 cubic phases were simulated by adding F atoms. According to Birch–Murnaghan calculations for structural optimization, both phases have a cubic crystalline structure with a space group Pm3m. The formation energy, mechanical, and thermodynamic studies all support the stability and synthesis of these materials. The Vienna ab initio simulation package (VASP) accurately determined the electronic band structures for α‐BeLiF 3 and β‐BeLiF 3 , revealing direct band gaps of 1.60 and 7.58 eV, respectively. The optical properties, including refractive index, optical conductivity, absorption coefficients, and reflectivity, have been calculated and analyzed, providing crucial insights into how these materials respond to different photon energies. The elastic constant was evaluated to meet the stability criteria, confirming the material's mechanical stability and ductility and highlighting the potential of BeLiF 3 for optoelectronic devices. Thermodynamic features, including sound velocity, Debye temperature, melting temperature, and compressibility, are calculated and compared. These combined structural, electronic, optical, mechanical, and thermodynamic results demonstrate that BeLiF 3 fluoroperovskites are promising candidates for industrial applications, especially in optoelectronics such as solar cells and UV‐protective smart windows. As a result, these findings can motivate additional computational and experimental studies.