DFT based first principles study of novel combinations of perovskite-type hydrides XGaH3 (X = Rb, Cs, Fr) for hydrogen storage applications

Hydrogen storage has become a challenge for researchers of this era because it is a cheap, clean, and non-pollutant element existing in nature. The current study has been performed in order to calculate the structural, electronic, optical, and magnetic properties of perovskite hydrides XGaH3 (X = Rb, Cs, Fr) through the Cambridge serial total energy package code based on density functional theory. The comprehensive investigations have been made while utilizing three cations (Rb, Cs, and Fr) in the cubic form of the ABH3 symmetry phase. The electronic properties of the considered hydrides have been investigated to determine bandgap, total density of states, and partial density of states, and their trends are devised against frequency (eV) of incident radiations. XGaH3 hydrides have shown metallic behavior because no energy bandgap is noticed near the Fermi level. The lattice constants of RbGaH3, CsGaH3, and FrGaH3 by utilizing the Perdew–Burke–Ernzerhof-Generalized Gradient Approximation (PBE + GGA) functional are found to be 4.0754 Å, 4.2137 Å, and 3.1237 Å. The local density approximation functional has also been used for calculations of lattice parameters, which are observed to be 3.9287 Å, 4.0673 Å, and 3.9818 Å, respectively. Anti-ferromagnetism is observed through magnetic analysis of the studied hydrides XGaH3 (X = Rb, Cs, Fr). Regarding the optical analysis, FrGaH3 is found to be a more suitable material for hydrogen storage. These novel materials exhibit minimum energy loss with maximum conductivity. The gravimetric ratio for hydrogen storage capacity is determined to be 2.5 wt. %, 2.0 wt. %, and 2.1 wt. % for RbGaH3, CsGaH3, and FrGaH3, respectively. The present computational calculations of these hydrides are attempted for the first time, which may provide exceptional improvements for applications in hydrogen storage.