First-principle quantum analysis of structural, electronic, optical, and mechanical properties of K3XH8 (X = Cr, Mn and Fe) hydrides for hydrogen storage system

Advancement of sustainable energy technologies depends on the development of stable and effective hydrogen storage materials. Here we explore the structural, electronic, optical, mechanical, and hydrogen storage characteristics of K₃XH₈ (X = Cr, Mn, Fe) perovskite-type hydrides using first-principles density functional theory (DFT) calculations. While electronic band structure and density of states (DOS) studies expose their metallic character, allowing hydrogen transport, the structural analysis guarantees the thermodynamic stability of these hydrides. Dielectric functions, refractive indices, absorption spectra, and reflectivity among other optical characteristics show their possible use in optoelectronics. Elastic constants confirm mechanical stability; additional investigation reveals that K₃CrH₈ and K₃MnH₈ display brittle behaviour whereas K₃FeH₈ is ductile. With computed desorption temperatures showing realistic application, hydrogen storage study demonstrates that K₃CrH₈, K₃MnH₈, and K₃FeH₈have gravimetric hydrogen storage capacities of 4.55 wt%, 4.47 wt%, and 4.45 wt% accordingly. These results offer a route towards the development of effective solid-state hydrogen storage technologies and give insightful analysis of the possibilities of perovskite hydrides for next-generation hydrogen storage systems.