First principles investigation of structural, elastic, thermoelectric, electronic and optical properties XH3 (X=Ac, La) for hydrogen storage

Efficient hydrogen storage is essential for its use as an energy source. Considering the various methods, hydrogen storage in solid materials shows great promise but requires further research. This study employs density functional theory using the Wien2k, with the LSDA method to determine the stability of this storage mode, and LSDA + mBJ to calculate the electronic, optical, and thermoelectric properties of AcH3 and LaH3. The electronic properties reveal that XH3 (X = Ac, La) exhibits a semiconducting nature with indirect energy gaps in both cases. The analysis of hydrogen storage properties determined the gravimetric hydrogen storage capacities for AcH3 and LaH3 to be 1.297 and 2.086 wt%, respectively. Calculations of the elastic constants validated the mechanical stability of these compounds. Thermoelectric characteristics, including electrical and thermal conductivity, Seebeck coefficient, electronic specific heat capacity, and Pauli magnetic susceptibility, have been evaluated, highlighting their p-type characteristics. The figure of merit indicates their potential for thermoelectric devices. Gravimetric ratios suggest significant hydrogen storage capacity, which could contribute to various transportation and energy applications.