First-principles investigation of the electronic and optical behavior with emphasis on charge density distribution in Cs2AgAuCl6 double halide perovskite

Abstract

The objective of this work is to explore the potential of the Cs₂AgAuCl₆ double halide perovskite for solar cell applications by systematically investigating its electronic structure, charge density, and optical properties. First-principles calculations were performed using the full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory, with the Tran–Blaha modified Becke–Johnson potential employed for accurate band gap estimation. The Brillouin zone was sampled with a 12 × 12 × 12 k-point mesh for ground-state properties and a denser 20 × 20 × 20 mesh for optical calculations, while the band structure was analyzed along an extended high-symmetry path (Γ–Δ–H–N–Σ–Γ–Δ–P) to capture the true conduction and valence band extrema. The results reveal that Cs₂AgAuCl₆ is an indirect band gap semiconductor (~0.40 eV) corresponding to the infrared spectral region, and exhibits strong optical absorption in the visible range. While Cs₂AgAuCl₆ has not yet been synthesized experimentally, similar double halide perovskites demonstrate the feasibility of such systems, and the present results may serve as a guide for future experimental realization. This work highlights the potential of Cs₂AgAuCl₆ as a sustainable and non-toxic material for next-generation optoelectronic and energy conversion applications.