First-principles study of properties of X3Sb2Au3 (X = K, Rb) ternary compounds for photovoltaic applications.

In this work, the structural, electronic, elastic, and optical properties of X₃Sb₂Au₃ (X = K, Rb) ternary compounds have been investigated using the density-functional theory method as implemented in the quantum espresso package. The generalized gradient approximation has been adopted in performing the calculations. The computed lattice parameters have been found to be in agreement with the available experimental and theoretical results. The K₃Sb₂Au₃ and Rb₃Sb₂Au₃ compounds have been found to be semiconductors with direct bandgaps of 1.236 eV and 1.353 eV, respectively. The compounds have also been found to be mechanically stable at zero pressure, ductile, and nearly metallic and therefore possess suitable attributes for industrial applications. The complex dielectric functions, absorption coefficients, reflectivity, refractive index, and energy loss spectra have also been presented. Refractive indices of 3.41 and 3.11 for K₃Sb₂Au₃ and Rb₃Sb₂Au₃ have also been calculated. The high refractive indices, high absorption coefficients, as well as the wide energy coverage of the absorption spectra, mostly in the ultraviolet–visible (UV–Vis) regions make the K₃Sb₂Au₃ and Rb₃Sb₂Au₃ compounds excellent UV–Vis light absorbers which are some of the essential characteristics for materials for photovoltaic applications. [ABSTRACT FROM AUTHOR]