First principal calculations for understanding physical properties and possible applications of vacancy ordered double perovskite Cs2ZrI6 (CZI)

First principal calculations are performed to understand structural, elastic, electronic, thermoelectric, thermodynamic and optical properties of inorganic vacancy ordered double perovskite, the Cs2ZrI6 (CZI). Calculated lattice constant of the rock-salt structured CZI shows closeness to that reported in the Materials Project Database. It exhibits mechanical stability, elastic anisotropy, brittleness, dominating ionic bonding, predominant stretching in chemical bonds, fair thermal stability and high melting temperature. It is an indirect band-gap (Gamma-X) semiconductor with a band-gap of 2.267eV, which would be suitable for fabricating low-cost tandem solar cells. Calculated thermoelectric properties predicted holes as the majority charge carriers and also shows its thermoelectric efficiency in the higher temperature region. Though, calculated specific heat at constant volume in the very low temperature region obeys the Debye's T3 law, it reaches the Dulong-Petit limit in the very high temperature region. The temperature and pressure dependence of some other thermodynamic parameters are also calculated in the present study. In terms of real and imaginary part of the dielectric function as well as some other auxiliary parameters, we have investigated the optical properties of the CZI and found its high optical absorbance capability in the far UV to extreme UV region of solar spectra.