Multifunctional halide double perovskites: Cs2AgMoCl6 and K2AgMoCl6 for renewable energy and spintronic technologies

In this study, we investigate the structural, elastic, electronic, magnetic, and thermoelectric properties of two halide double perovskites, Cs₂AgMoCl₆ and K₂AgMoCl₆, using first-principles calculations based on density functional theory (DFT). The calculations employ the full-potential linearized augmented plane wave (FP-LAPW) method within the GGA-PBE, GGA + U, and TB-mBJ approximations. Our findings reveal that both compounds crystallize in a stable cubic structure with space group Fm͞3m and exhibit ferromagnetic stability. The calculated electronic band structures and density of states, reveal half semiconducting (HSC) ferromagnetic (FM) behavior, with significant contributions from Mo-d orbitals to the valence and conduction bands, characterized by significant spin-splitting gap states, indicating potential for spintronic applications. Mechanical property analysis shows that the materials are anisotropic and ductile, making them suitable for flexible optoelectronic applications. Negative formation energy values support their synthesis viability. Additionally, thermoelectric property calculations show that Cs₂AgMoCl₆ and K₂AgMoCl₆ exhibit improved electrical conductivity, low thermal conductivity, high Seebeck coefficients and a figure of merit (ZT) approaching 1.0 over a temperature range of 200K–900K, suggesting their potential for applications in thermoelectric sensors and energy conversion devices. This work provides a comprehensive understanding of the physical properties of Cs₂AgMoCl₆ and K₂AgMoCl₆, highlighting their potential for use in renewable energy technologies, spintronics, and thermoelectric devices.