First-principles investigation of the structural, electronic, thermal, and mechanical properties of radium-based halide perovskites: A DFT study

Halide perovskites have become a remarkable and flexible material group for new optoelectronic technologies because of their extraordinary structural adaptability and various physical properties. A detailed first-principles examination is opened to checking the structural, electronic, mechanical, and optical traits of lead-free RaBX3 (B = Ag and Cu; X = Cl and Br) perovskites, thereby positioning them as principal radium-based candidates for advanced optoelectronic applications. The calculated Goldschmidt tolerance factors (0.832–0.962), along with very negative formation enthalpies that range from −3.22 to −3.73 eV/atom, undoubtedly confirm their excellent thermodynamic stability and structural strength in the cubic perovskite phase. Upon electronic structure analysis, it is predicted that RaCuCl3 and RaCuBr3 exhibit indirect bandgaps with high electronic activity, whereas RaAgCl3 and RaAgBr3 possess semiconductor bandgaps suitable for integration into optoelectronic devices. Mechanical property evaluations reveal ductile behavior, moderate stiffness, and anisotropy, indicating good mechanical reliability and compatibility with flexible device architectures. The optical absorption of these materials in the visible and ultraviolet regions is very high and reaches as much 3.8 × 105 cm−1 for the absorption coefficient, which is comparatively supported by significant dielectric responses, particularly in RaCuBr3 optimized refractive indices. Charge population analysis suggests the existence of ionic bonding as the main characteristic, while the Cu-based compounds have more covalent character, thus making it possible to tailor the electronic and magnetic properties through compositional engineering. Overall, the present study identifies RaBX3 perovskites as promising lead-free materials for solar energy harvesting, energy storage, and multifunctional optoelectronic technologies.