First-Principles Study on Physical Properties of Perovskite XZrH ₃ (X = Cs, Pd, Ru) Hydrogen Storage Materials

In recent years, perovskite-type hydrides have emerged as a research hotspot in hydrogen storage materials, offering a viable solution to the global energy crisis. This study employs first-principles calculations to systematically investigate the structural, electronic, optical, mechanical and thermodynamic properties of novel perovskite hydrides XZrH 3 (X [Formula: see text] Cs, Pd, Ru). The calculated lattice parameters of XZrH 3 (X [Formula: see text] Cs, Pd, Ru) are 4.34[Formula: see text]Å, 3.74[Formula: see text]Å and 3.68[Formula: see text]Å, respectively, all adopting a cubic structure with the Pm-3m space group. Electronic band structure and density of states (DOS) analyses reveal that all three compounds exhibit metallic characteristics, as their valence and conduction bands overlap at the Fermi level. Hydrogen storage performance evaluations show gravimetric hydrogen storage capacities of 1.33[Formula: see text]wt.%, 1.51[Formula: see text]wt.% and 1.55[Formula: see text]wt.% for CsZrH 3 , PdZrH 3 and RuZrH 3 , respectively. They are comparable to other investigated perovskite hydrides (SrCuH 3 , 1.9[Formula: see text]wt.%; CsTiH 3 , 1.6[Formula: see text]wt.%), and outperform some Zr-based systems like BaZrH 3 (1.31[Formula: see text]wt.%). Negative formation enthalpies confirm their thermodynamic stability, which is further supported by phonon calculations — CsZrH 3 and PdZrH 3 exhibit no imaginary frequencies, indicating dynamical stability, while RuZrH 3 shows inherent dynamical instability. Desorption temperatures are calculated as 908[Formula: see text]K, 974[Formula: see text]K and 612[Formula: see text]K, respectively. Although the gravimetric capacity of these three hydrides remains below the 2025 U.S. DOE target (5.5[Formula: see text]wt.%), they exhibit a favorable balance of high capacity and desorption temperature. Mechanical property analyses demonstrate that all compounds satisfy the Born elastic stability criteria, confirming structural stability. They exhibit anisotropic behavior, with CsZrH 3 and PdZrH 3 classified as ductile ([Formula: see text]) and RuZrH 3 classified as brittle ([Formula: see text]). Optical property studies highlight PdZrH 3 ’s superior performance, including a higher absorption coefficient and lower reflectivity compared to the other two compounds, suggesting potential for solar cells and sensors. These findings collectively indicate that XZrH 3 (X [Formula: see text] Cs, Pd, Ru) perovskite hydrides are promising candidates for hydrogen storage applications in the green energy economy.