A comparative ab initio analysis of the stability, electronic, thermodynamic, mechanical, and hydrogen storage properties of SrZnH3 and SrLiH3 perovskite hydrides through DFT and AIMD Approaches

Abstract

Recently, perovskite hydrides have gained attention as potential solid-state storage materials due to their safety and higher density. In this paper, the Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD) was used to investigate the stability, electronic, mechanical, thermodynamic, and hydrogen storage properties of SrLiH 3 and SrZnH 3 hydride-types. The structural characteristics demonstrate that these materials exhibit a cubic phase with SrZnH 3 has the higher volume due it is higher lattice constant of 3.9 Å, compared to LiSrH 3 (3.81 Å). The phonon dispersion curves and formation energy values revealed that both compounds are dynamically and thermodynamically stable. AIMD simulations further demonstrate the thermal stability of these compounds, revealing no structural deformation over a simulation time of 10 ps. The electronic band structure and density of states analysis show a band gap of 1.85 eV using GGA (2.57 eV using HSE06) for SrLiH 3 , while SrZnH 3 displays metallic behavior due to the absence of a band gap. In terms of hydrogen storage capacity, SrLiH 3 exhibits a superior gravimetric capacity of 3.1 wt%, compared to 1.94 wt% for SrZnH 3 . Additionally, we analyzed various thermodynamic properties, including free energy , enthalpy, zero-point energy, entropy, and specific heat capacity at different temperatures, providing a comprehensive understanding of material behavior under various conditions. The Pugh's ratio and Cauchy pressure indicate that SrZnH 3 demonstrates ductile behavior, while SrLih 3 exhibits a brittle nature. Moreover, the Born criteria and three-dimensional illustrations of elastic properties confirm that both compounds are mechanically stable and exhibit anisotropic characteristics. These results suggest that SrLiH 3 is a good candidate for applications requiring medium hydrogen storage capacity, while SrZnH 3 is better suited for scenarios demanding efficient hydrogen transportation. • SrLiH 3 shows a band gap of 1.85 eV (GGA) and 2.57 eV (HSE06), SrZnH 3 is metallic. • SrZnH 3 and SrLiH 3 are thermodynamically and dynamically stable perovskite hydrides. • Mechanical analysis shows SrZnH 3 is ductile, while SrLiH 3 exhibits brittleness. • SrLiH 3 has a hydrogen storage capacity of 3.1 wt%, SrZnH 3 supports rapid diffusion. • AIMD simulations confirm the structural and thermal stability of both compounds.