Tailoring the physical and hydrogen storage properties of thermodynamically stable XSc3H8 (X= Li and Na) hydrides for the hydrogen storage application

Emphasizing their structural stability, metallic behaviour, and hydrogen storage capacity, this paper investigates the multifunctional potential of scandium-based XSc₃H₈ (X = Li and Na) hydrides using density functional theory (DFT), as well as their appropriateness for specialized applications including energy storage systems, catalysis, and electronic devices where small-scale, high-performance materials are desired despite scandium's high cost. The mechanical stability of both compounds is confirmed by the optimized elastic constants satisfying Born's criterion. With LiSc₃H₈ showing more stiffness, Poisson's ratio values point to a ductile character, and positive bulk and shear moduli imply significant mechanical hardness. While phonon dispersion verifies dynamic stability, electronic band structure investigation uncovers metallic behaviour. Strong UV absorption and high reflectivity seen in optical studies suggest possibility for photonic uses. With gravimetric capacities of 5.38 wt% for LiSc₃H₈ and 4.86 wt% for NaSc₃H₈, hydrogen storage study shows both compounds above the U.S. Department of Energy's 2020 objective. LiSc₃H₈ is the most promising contender as it has a lower desorption temperature (447.2 K) than NaSc₃H8 (465.5 K). These results imply that XSc₃H₈ (X = Li and Na) hydrides are possible candidates for hydrogen storage next generation.