Electronic, Optical and Thermoelectric Properties of Stable A2LiIO6 (A = Sr, Ba) Lead-Free Double Perovskites for Low-Cost Energy Applications

The new halogen-based non-toxic oxide double perovskites A2BIO6 compounds have attracted considerable research due to their excellent electronic, optical, and thermoelectric properties. To be part of this research interest, we have investigated A2LiIO6 (A = Sr, Ba) double perovskites for their structural, electronic, optical, and thermoelectric properties on the basis of first-principles calculations. Both compounds were found thermodynamically and dynamically stable from the values of Gibbs free energies and positive phonon frequencies. The structural stability of both the A2LiIO6 compounds was confirmed by optimum of tolerance factors. The Canband structure show direct band gaps with a value of 2.65 eV for Sr2LiIO6 and 2.08 eV for Ba2LiIO6 with modified Becke and Johnson potential. The absorption spectra for both double perovskites was found in the visible part of the electromagnetic spectrum. The reflectivity was predicted below 30