Multifaceted exploration of structural, optoelectronic, mechanical, bader charge, phononic, and hydrogen storage properties of novel Li-based hydrides for energy applications

To combat climate change and the energy issue, scientists are devoting a great deal of their resources to researching and creating hydrogen storage systems. We investigated the optoelectronic, transport, and hydrogen storage characteristics of XMgNiH₄ (X = Ba, Li) in the framework of density functional theory. We computed the dielectric function, refractive index, extinction coefficient, and energy loss function using Kramer-Kroning relations. The findings show that XMgNiH₄ (X = Ba, Li) is an excellent material for hydrogen storage. Both materials studied have hydrogen storage capabilities with 6.6 wt% and 8.1 wt% gravimetric ratios, respectively. The electronic properties indicate hybridization resulted from interactions between the Ni-d, Li-s/p, Ba-s, and H-p orbitals, indicating direct bandgaps (2 eV) semiconducting materials. The electronic charge density revealed a semiconductor with mixed bonds, low ionicity, and high covalence. Boltztrap code is used to examine the thermoelectric properties of these materials, including the Seebeck coefficient, the power factor, and the figure of merit based on Semi-classical Boltzmann theory. The class of high-efficiency thermoelectric materials (TE) for high-temperature application domains, as indicated by their high Seebeck coefficient and figure of merit values. These discoveries open new opportunities for researchers investigating the possible applications of these materials in thermoelectric and optoelectronic devices.