Abstract
The study of physical characteristics of lead-free double perovskites A2SnI6 (A = Cs, Rb) are investigated via density functional theory. The mechanical conductions are satisfied by Born criteria and their ductile nature by Poisson (>0.26) and Pugh's ratios (>1.75). The 1.147 eV and 1.197 eV are the calculated direct band gap values for Cs2SnI6 and Rb2SnI6. Optical properties are examined in terms of refractive index, absorption coefficient, and dielectric constants. Threshold energies closer to bandgaps have absorption in the visible region of the spectrum. The thermoelectric properties are analyzed by electrical conductivity, thermal conductivity, Seebeck coefficient, power factor, and figure of merit. ZT calculations demonstrate minute variation in the temperature range of 200-800K. The thermodynamic properties are discussed by specific heat capacity, Hall effect, susceptibility, and electron density. The p-type semiconducting nature of the studied compounds has been predicted by transport properties analysis.