First-principles evaluation of the structural, electronic, optical, and thermodynamic properties of LiSnI ₃ perovskite

This study presents a comprehensive first-principles (DFT) investigation of the structural, electronic, optical, and thermodynamic properties of the LiSnI 3 perovskite. Structural optimization confirms a stable cubic LiSnI 3 perovskite phase with a lattice constant of 6.22 Å and a bulk modulus of 16.77 GPa, supported by a negative formation energy (−1.35 eV/atom). Electronic structure calculations show that LiSnI 3 is a direct-band-gap semiconductor, with band gaps of 0.33 eV (GGA-PBE) and 0.76 eV (HSE06). The optical properties of LiSnI 3 reveal a strong static dielectric response (ε₁ (0) = 8.08), a high refractive index (n (0) = 2.84), and a pronounced absorption edge at 0.81 eV, demonstrating suitability for infrared and UV optoelectronic applications. Thermodynamic results, combined with ab initio molecular dynamics simulations, confirm that the LiSnI 3 perovskite remains dynamically and thermally stable across broad pressure and temperature ranges. The combined findings highlight LiSnI 3 as a promising lead-free perovskite material for advanced optoelectronic and energy-related applications.