First-Principles and AIMD Investigation of Physical Properties and Hydrogen Storage Performance of Dynamically Stable ATiH3 (A = Ca, Sr, and Ba) Perovskite Hydrides

Abstract

This study presents a comprehensive first-principles investigation of the ATiH₃ (A = Ca, Sr, and Ba) perovskite hydride series using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations to evaluate their potential for solid-state hydrogen storage. Structural optimization confirmed that all three compounds are thermodynamically stable with cubic symmetry, while phonon dispersion and AIMD simulations verified their dynamical and thermal stability. Electronic structure calculations using generalized gradient approximation–Perdew–Burke–Ernzerhof (GGA–PBE) and HSE06 functionals revealed metallic behavior in CaTiH₃, SrTiH₃, and BaTiH₃, which is favorable for hydrogen diffusion and reversible hydrogen release. Mechanical analysis indicated a gradual transition from the relatively brittle and rigid CaTiH₃ to the more ductile BaTiH₃ with increasing A-site ionic radius, whereas optical calculations demonstrated strong ultraviolet absorption and high reflectivity at low photon energies. Hydrogen storage analysis showed that CaTiH₃, SrTiH₃, and BaTiH₃ exhibit gravimetric hydrogen storage capacities of 3.299, 2.166, and 1.594 wt% and volumetric capacities of 91.60, 89.90, and 73.30 g H₂ L⁻¹, respectively. Among them, CaTiH₃ is identified as the most promising candidate because its lower host-lattice molar mass results in the highest hydrogen storage capacity, while its stronger interatomic bonding, highest negative formation energy, greater lattice rigidity, and superior thermal stability provide a robust framework for hydrogen storage. These findings demonstrate that CaTiH₃ offers the best overall balance between structural stability and hydrogen storage performance, making it the most promising member of the ATiH₃ series for future solid-state hydrogen storage applications.