Electronic, magnetic, optical, and thermoelectric properties of K2OsCl6 for spintronic and energy harvesting applications

Abstract

We report a comprehensive first-principles study of the structural, electronic, magnetic, optical, and thermoelectric properties of the double perovskite K2OsCl6 using density functional theory (DFT) within the generalized gradient approximation (GGA). The calculations predict a ferromagnetic ground state with a total magnetic moment of similar to 1.99 mu B per formula unit, largely arising from Os atoms (similar to 1.33 mu B). Spin-resolved electronic band structures reveal robust half-metallicity, featuring a metallic majority-spin channel and a direct minority-spin band gap of similar to 0.8 eV, yielding nearly 100% spin polarization at the Fermi level. The optimized lattice constant of 10.45 angstrom shows excellent agreement with experimental data. Optical analysis demonstrates strong spin-dependent behavior in the visible and ultraviolet regions, with a peak absorption coefficient of similar to 1.5 x 10(5) cm(-1) at 6 eV and static dielectric constants of 4.2 (spin-up) and 3.8 (spin-down). The refractive index exhibits anomalous dispersion, reaching refractive index values up to 2.8 in the visible range. Thermoelectric calculations indicate a Seebeck coefficient of similar to 180 mu V/K at 900 K, electrical conductivity of 4.5 x 10(5) Omega(-1) m(-1), and low thermal conductivity of 2.8 W m(-1) K-1 at room temperature.