Physical properties of the ternary K 3 NaH 4 compound by DFT simulations

The potential of ternary hydrogen-based alloys in hydrogen storage and energy systems has attracted much interest. These systems are essential for the advancement of clean and sustainable energy technologies. 2.80 w% was found to be the gravimetric hydrogen storage capability of the K3NaH4. Using first-principles calculations and the GGA-PBE + SOC technique, a theoretical analysis of the structural features, phonon dispersion, elastic constants, as well as the electronic, optical and thermoelectric characteristics of K3NaH4 was carried out. The optimized lattice parameter is 5.531 Å, and the material exhibits a direct band gap of 2.35 eV, indicating a nonmagnetic semiconducting behavior. Optical properties such as the refractive index, optical conductivity, extinction and absorption coefficients, and dielectric constants were analyzed. The absorption onset at 2.35 eV, high refractive indices and strong ultraviolet absorption confirm the material’s suitability for optoelectronic applications. Thermoelectric transport calculations using BoltzTraP reveal a maximum ZT of 3.12 and a Seebeck coefficient of 237 μV/K at 1000 K, suggesting that K3NaH4 is a promising candidate for high-performance thermoelectric devices.