AB-initio study of electronic, elastic, and optical properties of double antiperovskite, Li6AgBiX2 (X = Cl, Br, I)

Abstract

In this study, several intriguing double antiperovskite (DAP) materials with amazing optoelectronic and photovoltaic properties have been investigated. Here, the structural, electronic, elastic, optical, thermal, and photocatalytic behavior of newly proposed double antiperovskites $L{i}_{6}AgBi{X}_2$ (where X = Cl, Br, and I) are thoroughly investigated using density functional theory (DFT). Firstly, the materials under study showed outstanding structural stability and mechanical characteristics including elastic constants (Cij), Young’s modulus (Y), bulk modulus (B), shear modulus (G), and Poisson’s ratio. Furthermore, the investigated materials exhibit remarkable electronic and optical characteristics, including electronic band structure, density of states, refractive index, extinction coefficient, dielectric function, and reflectivity. For $L{i}_{6}AgBi{X}_2$ (X = Cl, Br, I), reduced bandgap values of 1.33 eV, 1.27 eV, and 1.21 eV have been reported, respectively. Optical characteristics display considerable light absorption coefficients in the infrared and visible light bands. The heat capacity ($C_V$) and Debye temperature (${\Theta }_D$) were computed for thermodynamic analysis. In this context, the redox potential and electron–hole recombination rate of the materials under investigation serve as key indicators of their photocatalytic properties, providing valuable insights into their ability to facilitate chemical reactions driven by light. Here, newly suggested double antiperovskites $L{i}_{6}AgBiC{l}_2$, $L{i}_{6}AgBiB{r}_2$, and $L{i}_{6}AgBi{I}_2$ having indirect reduced band gap values less than the parent organic–inorganic perovskite MAPI ($E_g$=1.6eV) and pre-existing double perovskite $L{i}_{2}AgBiB{r}_6$ ($E_g$=2.124eV for PBE0 potential). So proposed materials are considered highly promising materials for practical use in solar cells due to their optimal energy gaps, mechanical stability and greater light absorption coefficient.