The DFT study of the structural, hydrogen, electronic, mechanical, thermal, and optical properties of KXH3 (X = Ca, Sc, Ti, & Ni) perovskites for H2 storage applications

Abstract In this study, we employ density functional theory calculations to comprehensively investigate the structural, electronic, hydrogen storage capacity, mechanical, thermal, and optical properties of KXH₃ (X = Ca, Sc, Ti, & Ni) hydride perovskites, unveiling their potential for H₂ storage applications. The lattice parameters, calculated using the GGA-PBE functional, are found to be 4.482 Å, 4.154 Å, 3.974 Å, and 3.686 Å for KCaH₃, KScH₃, KTiH₃, and KNiH₃, respectively. Interestingly, the electronic structure analysis reveals that while KScH₃, KTiH₃, and KNiH₃ exhibit metallic behavior, KCaH₃ stands out as a semiconductor. Population analysis indicates that these compounds possess a strong potential for hydrogen storage due to their strong bonding and long bond lengths. Furthermore, the investigation of dynamic and mechanical stability suggests that the studied materials are promising candidates for experimental synthesis, as they exhibit both thermodynamic and mechanical stability. Gravimetric analysis reveals promising hydrogen storage capacities of 3.646 wt%, 3.452 wt%, 3.346 wt%, and 3.005 wt% for KCaH₃, KScH₃, KTiH₃, and KNiH₃, respectively. The calculated hydrogen desorption temperatures are 442.40 K for KCaH₃, 518.68 K for KScH₃, 592.47 K for KTiH₃, and 614.82 K for KNiH₃, indicating the suitability of these materials for hydrogen storage applications within practical operating temperature ranges. Novelty Statement: In this study, we present a comprehensive theoretical investigation of the novel perovskite materials KXH₃(X = Ca, Sc, Ti, Ni), encompassing their structural, electronic, hydrogen storage, mechanical, thermal, and optical properties. To the best of our knowledge, this is the first report providing insights into these unexplored compounds, as no previous theoretical or experimental studies have been conducted on them.