A pressure tunable optical and thermoelectric properties of Rb2CuSbX6 (X = cl, Br, and I) by FPLAPW+lo method

Abstract

The pressure dependencies of the structural, electrical, elastic, optical, and thermoelectric characteristics of the Halide double perovskites (HDPs) Rb2CuSbX6 (X = Cl, Br, and I) compounds were computed using the FP-LAPW method within the density functional theory framework, under high pressure conditions. HDPs received a lot of attention due to their potential application in optoelectronic and thermoelectric devices. The Perdew-Burke-Ernzerhof (PBEsol-GGA) is used to investigate the structural properties of selected compounds, while the modified Becke-Johnson (mBJ) functional is used to obtain a better agreement between the calculated optoelectronic and electronic properties and experimental observations. The Born criteria and formation energy are explored for the stability of all selected HDPs. The elastic constants of cubic symmetry are investigated to determine the difference between ductile and brittle nature, anisotropy, and bulk modulus. The bandgaps for Rb2CuSbCl6, Rb2CuSbBr6, and Rb2CuSbI6 are 1.08 eV, 0.72 eV, and 0.33 eV, respectively. Decrease band gap with increase in pressure. The density of states plots under zero pressure exhibit a combination of ionic and covalent bonding, whereas an increase in pressure results in a reinforcement of covalent bonding. The absorption spectra are observed in the infrared region. All HDPs were further analyzed with respect to optical absorption, refractive index, and dielectric constants for the energy range 0–10 eV. Additionally, Boltzmann classical theory explains the lower lattice temperature, greater Seebeck coefficient, thermal conductivity, and electrical conductivity of HDPs, making them for thermoelectric applications.