Ab initio study of structural, optoelectronic, magnetic, and mechanical properties of Cs2KXBr6 (X = Mo, W): HDPs for spintronic and energy applications

Abstract

Abstract The structural, optoelectronic, magnetic, and mechanical investigations of Cs 2 KXBr 6 (X = Mo & W); halide double perovskites (HDPs), in the Fm-3m space group, have been conducted via an ab initio study. The formation energies per atom (eV) of Cs 2 KMoBr 6 and Cs 2 KWBr 6 are found to be − 1.72 and − 1.81, respectively. To reveal the accurate energy band gaps of the materials, the TB-mBJ potential is utilized. The electronic analysis reveals that both materials exhibit semiconducting behavior in both spin channels. The energy band gaps of Cs 2 KMoBr 6 are 1.7 eV (up-spin) and 2.8 eV (down-spin), and Cs 2 KWBr 6 are 1.6 eV (up-spin) and 3.3 eV (down-spin). The Phonon dispersion analysis and ab initio molecular dynamics simulations reveal the dynamical stability of the materials. The ferromagnetic (FM) and antiferromagnetic (AFM) natures of Cs 2 KWBr 6 and Cs 2 KMoBr 6 have been predicted, respectively. The net magnetic moment (µ B ) of the ground state of Cs 2 KWBr 6 and Cs 2 KMoBr 6 is 3 and 0, respectively. The mechanical analysis reveals that Cs 2 KWBr 6 exhibits higher structural stability compared to the Cs 2 KMoBr 6 material. The computed optical properties indicate that the materials have high absorption with a maximum of 140 cm −1 at 13.5 eV, a peak refractive index of 1.9 between 4.5 and 5.8 eV, and a maximum reflectivity of about 0.40 at high energy, which makes them promising candidates for high-energy region and moderate refractive indices, suggesting potential relevance for optoelectronic applications. In addition, the spin-dependent electronic structure and magnetic ordering indicate possible applicability in spin-dependent electronic systems. However, further device-level investigations are required to fully assess their technological performance.