Unlocking Stability and Efficiency in Double Inorganic Halide Perovskite Cs2KMoX6 (X = Cl, I) Materials Through First Principles Study

The physical properties of halide double-perovskites (HDPs) Cs₂KMoX₆ (X = Cl, I) were investigated based on density functional theory (DFT). The Perdew, Burke, and Ernzerhof generalized-gradient approximation (PBE-GGA) and modified Becke-Johnson (mBJ) potential were applied in the study. The enthalpy of formation (ΔH) was computed to be − 0.637 eV for Cs₂KMoCl₆ and − 1.57 eV for Cs₂KMoI₆, confirming the stability of Cs₂KMoX₆ (X = Cl, I) with negative values. The ferromagnetic (FM) properties were confirmed by observing whole number values of the total magnetic moment (µ_B), measuring 2.99 µ_B for Cs₂KMoCl₆ and 3.00 µ_B for Cs₂KMoI₆. Cs₂KMoCl₆ exhibits a direct band gap of 4.85 eV (down spin) and 3.16 eV (up spin), while Cs₂KMoI₆ shows 2.66 eV (down spin) and 2.19 eV (up spin), confirming their semiconductor characteristics. Optical features revealed the UV absorption in both perovskites, with energy values of 9.69 eV for Cs₂KMoCl₆ and 10 eV for Cs₂KMoI₆. Both Cs₂KMoCl₆ and Cs₂KMoI₆ satisfy the Born stability criteria, indicating their mechanical stability and suitability for practical applications. Additionally, thermoelectric features were evaluated utilizing the BoltzTraP code. The largest Seebeck coefficient value is 1.81 × 10⁴ µV/K at 300 K for Cs₂KMoCl₆ and 1.84 × 10⁴ µV/K at 300 K for Cs₂KMoI₆. Findings suggest that both Cs₂KMoX₆ (X = Cl, I) exhibit promising potential for usages in thermoelectricity, optics, and data storage.