Structural, electronic, elastic, optical and thermoelectric properties of ASiCl₃ (A = Li, Rb and Cs) chloroperovskites: a DFT study

Chloroperovskites have attracted considerable attention in recent years as promising candidates for various technological applications. Their appeal lies in their appropriate optical bandgap, outstanding chemical stability, abundant availability on Earth, and non-toxic nature. In this work, we have investigated the structural, electronic, elastic, optical and thermoelectric properties of ASiCl₃ (A = Li, Rb and Cs) using density functional theory. The Tran–Blaha modified Becke Johnson (TB-mBJ) potential were used for exchange–correlation. The band structure profiles of the LiSiCl₃, RbSiCl₃ and CsSiCl₃ materials reveal a semiconductor nature with a small direct band gap of 0.28, 0.37 and 0.54 eV, respectively. The obtained negative values for formation and cohesive energies affirm the energetic and dynamic stability of these compounds. The elastic constants and mechanical parameters acquired suggest that the compounds are mechanically stable and demonstrate a ductile nature with by low stiffness. The analysis of optical parameters revealed an increasing trend in the dielectric constant, refractive index, reflectivity, and absorption coefficient in the UV domain as the A-site atom transitions from Li to Rb and then to Cs (decreasing electronegativity). In the visible spectrum, the three chloroperovskites exhibit low reflectivity, while the highest absorption coefficient is assigned to the CsSiCl₃ in the UV domain. The thermoelectric properties are computed with respect to chemical potential at various temperatures. At room temperature, the merit factors for CsSiCl₃, RbSiCl₃, and LiSiCl₃ are 0.95, 0.84, and 0.80, respectively, indicating their potential suitability for use in thermoelectric devices.