Excellent hydrogen storage capabilities and optoelectronic attributes of XClH (Li, Na, and K) perovskite hydrides for green energy technologies.

The high hydrogen storage capacity, stability, and reversibility of perovskite hydrides make them promising materials for the energy industry. They play a vital role in sustainable energy technologies, including fuel cells and hydrogen storage systems. This work offers a comprehensive understanding of the physical attributes of XClH (X = Li, Na, and K), utilizing the DFT-based Wien2K code. The quantum mechanical effects, along with Coulombic repulsions, are incorporated using the mBJ functional. For the assessment of the structural and thermo-dynamical integrity of XClH (X = Li, Na, and K), optimization curves, tolerance factors, and formation energies are evaluated. The second ordered stress energy tensor is employed to compute the elastic constants of cubic XClH (X = Li, Na, and K). The electronic properties are analyzed, which revealed indirect bandgaps of 0.29 eV, 0.55 eV, and 1.87 eV for LiClH NaClH and KClH, respectively. The electromagnetic interaction depicts that the studied hydrides possess higher divergence and dispersion in the visible range. The gravimetric densities for LiClH, NaClH, and KClH are obtained as 10.97 wt%, 8.38 wt%, and 6.92 wt%, respectively, which exceed the criteria mentioned by the US DOE for 2025, making these materials excellent contenders for renewable energy and hydrogen storage.