DFT analysis of structural, electronic, optical, and thermodynamic properties of LiXI3 (where X = Ca, Sr, Ba) halide perovskites for optoelectronics

This paper presents a comprehensive investigation of the structural, electronic, mechanical, optical, and thermodynamic properties of LiXI₃ (X = Ca, Sr, Ba) alkali-based single halide perovskites using DFT-based first-principles calculations for the first time. This cubic perovskite structure, LiXI₃ (X = Ca, Sr, Ba), exhibits positive phonon dispersion curves, confirming these compounds' dynamical stability. Analysis of the electronic band structure and density of states reveals that LiXI₃ (X = Ca, Sr, Ba) are indirect band gap semiconductors with band gap values determined using GGA (HSE06) are 2.363 (3.475) eV, 2.363 (3.623) eV & 2.350 (3.698) eV for LiCaI₃, LiSrI₃, and LiBaI₃, respectively. The optical properties of LiXI₃ compounds (X = Ca, Sr, Ba) were analyzed, focusing on the dielectric function, absorption coefficient, conductivity, reflectivity, refractive index, and loss function. The study revealed a broad absorption spectrum, high dielectric function, and refractive index at low energy states, along with high conductivity and low loss function and reflectivity, highlighting their potential for use in electronic and optoelectronic devices. The elastic constants were assessed to fulfill stability criteria, confirming the solids mechanical stability and ductility. The Zener anisotropy index (A_z) and equivalent anisotropy (A^eq) were calculated, and three-dimensional diagrams of elastic moduli were generated using the ELATE tool, indicating that our studied compounds display anisotropic behavior. Additionally, the low thermal conductivity and Debye temperature suggest that LiXI₃ (X = Ca, Sr, Ba) are suitable for thermal barrier coating material. Overall, these alkali-based halide perovskites exhibit promising applications in optoelectronics and semiconductors.