First principle calculations are carried out to investigate the structural, electronic and optical properties of cubic perovskites CsSnM3 (M = Cl, Br, I). The theoretically calculated lattice constants are found to be in good agreement with the experimentally measured values as compared to previous calculations. It is found that these perovskites are direct band gap semiconductors. The electrons densities reveal strong ionic bonding between Cs and halide cations while strong covalent bonding between Sn and halide cations. Optical properties of these compounds like real and imaginary parts of the dielectric functions, refractive indices, extinction coecients, reectivities, optical conductivities and absorption coecients are calculated. The direct band gap nature and high absorption power of these compounds in the infrared, visible and ultraviolet energy range predicts that these perovskites can be used in optical and optoelectronic devices working in this range of the spectrum.
The modified Becke-Johnson exchange potential approximation is applied to predict the band structure, optical parameters and electron density of SnMg2O4 and SnZn2O4. The local density approximation, generalized gradient approximation (GGA), EV-GGA significantly underestimate the direct band gap values compared to modified Becke-Johnson approximation. The band gap dependent optical parameters such as dielectric constant, index of refraction, reflectivity, and optical conductivity are calculated and analyzed. A prominent feature of cation replacement is observed and analyzed for these studied compounds. The replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical parameters. This variation is of crucial importance for device fabrication in different regions of the spectrum.
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