Unraveling the complexities of A2NaMoCl6 (A=Cs, Rb) halide double perovskites through theoretical methods

Abstract

This study explores the structural, electronic, magnetic, optical, mechanical and thermoelectric (TE) properties of halide double perovskites (HDPs) A₂NaMoCl₆ (A = Cs, Rb) using density functional theory (DFT). The magnetic features of A₂NaMoCl₆ (A = Cs, Rb) showed that the total magnetic moments of 12.75181μ_B and 12.74960 μ_B, respectively. The stable nature of cubic A₂NaMoCl₆ (A = Cs, Rb) is supported by calculating the formation enthalpy (ΔH) and tolerance factor(τ). The negative ΔH values and τ values within stability range confirmed the stable nature of structure. Spin-polarized band structure (BS) and density of states (DOS) analysis show that Rb₂NaMoCl₆ and Cs₂NaMoCl₆ are direct bandgap semiconductors. Additionally, the optical properties including the absorption coefficient (α(ω)), real (ɛ₁(ω)) and imaginary (ɛ₂(ω)) components of the dielectric function ε(ω), optical conductivity (σ(ω)), refractive index (n(ω)), energy loss (L(ω)) and reflectivity (R(ω)) were also evaluated. Because of their large absorption and small reflectivity in the UV-VIS range, these HDPs possess considerable potential for applications in optoelectronic devices. In addition, we have also analyzed the thermoelectric properties which revealed that Cs2NaMoCl6 achieve higher efficiency with ZT value of over 0.8 at room temperature which signifies the importance of current study.