First-principles study of Cs3SbX6 (X = F, Cl) for scintillation and optoelectronic applications

Abstract

This work investigates the structural, elastic, optoelectronic and thermodynamic features of novel ternary halide double perovskites Cs₃SbX₆ (X = F, Cl) using density functional theory (DFT) paradigm. The lattice parameters of these ternary halide DPs Cs₃Sb(F/Cl)₆ were determined to be 10.12 Å and 11.89 Å, respectively. The energy bandgap was calculated using PBE-GGA in conjunction with the TB-mBJ exchange-correlation functional. The ternary halide double perovskite containing F exhibited an elevated band gap value attributable to the enlargement of halide anion size. The inverse relation between bandgap and lattice parameters indicates that an increase in lattice constant leads to a reduction in the electronic band gap. The estimates of the DOS have elucidated the characteristics of the electronic states that contribute to the formation of energy bands. The optimal light yield (LY) under ideal circumstances is measured at 106411.28 ph/MeV for Cs₃SbF₆ and 123304.56 ph/MeV for Cs₃SbCl₆, indicating its prospective use in scintillating devices. Additionally, the optical characteristics, including complicated $\epsilon \left(\omega \right)$, absorption coefficients $\alpha \left(\omega \right)$, reflectivity $R\left(\omega \right)$, and refractive index $n\left(\omega \right)$, are calculated for these newly proposed composites. The computed thermodynamic parameters indicate a negative Gibbs Free Energy (G) and an increase in the heat capacities of these compounds, demonstrating their stability. A comprehensive investigation of the optical properties indicates that Cs₃SbX₆ (X = F, Cl) is a promising candidate for high-energy radiation detection and many optoelectronic applications.