Theoretical investigation of elastic and optoelectronic properties of barium-based Halide perovskites KBaI₃ and RbBaI₃

Abstract The objective of this study is to evaluate the structural, electronic, elastic, and optical characteristics of Ba-based halide perovskites KBaI 3 and RbBaI 3 . Our investigation utilized the full-potential linearized augmented plane wave approach (FP-LAPW) with the PBE-GGA (Perdew–Burke–Ernzerhof generalized gradient approximation). To calculate the electronic band structures, we employed the TB-mBJ (Tran–Blaha modified Becke–Johnson) potential. The structural parameters were found to be in reasonable agreement with available data. Both compounds exhibit an indirect band gap (R-Γ), with estimated band gap values of 5.019 eV for KBaI 3 and 4.997 eV for RbBaI 3 using the TB-mBJ potential. For the first time, the elastic properties, as well as the real and imaginary parts of the dielectric function and other optical constants of KBaI 3 material have been determined. The predicted elastic constants indicate that both materials are mechanically stable. The Pugh ratio, Poisson’s ratio and Cauchy pressure values further suggest that the compounds are ductile. The optical properties, including the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, absorption coefficient, and reflectivity, have been analyzed and discussed.