First principles exploration of high hydrogen storage capacity of lithium-based perovskite hydrides

Abstract Context The search for efficient solid-state hydrogen storage materials is essential for advancing clean energy technologies. In this work, Li-based perovskite hydrides (LiBH 3 , LiCuH 3 , LiMgH 3 , and LiSiH 3 ) are studied using first-principles calculations. All compounds show negative formation energies, indicating thermodynamic stability. LiBH 3 , LiCuH 3 , and LiMgH 3 are dynamically stable, while LiSiH 3 is unstable due to imaginary phonon modes. Mechanical analysis confirms stability for all systems, with LiCuH 3 and LiMgH 3 showing higher rigidity. Electronic properties reveal metallic behavior for LiBH 3 , LiCuH 3 , and LiSiH 3 , while LiMgH 3 is semiconducting with a 2.59 eV band gap. Hydrogen storage capacities are 14.56 wt% for LiBH 3 , 4.11 wt% for LiCuH 3 , 8.82 wt% for LiMgH 3 , and 7.95 wt% for LiSiH 3 . LiCuH 3 also shows the lowest desorption temperature (382.7 K), indicating favorable kinetics. Methods All calculations were performed within the framework of density functional theory (DFT) using the Quantum ESPRESSO package. The exchange–correlation energy was treated using the generalized gradient approximation in the Perdew–Burke–Ernzerhof (GGA-PBE) form, and electron–ion interactions were described using ultrasoft pseudopotentials. Valence configurations included Li (2s 1 ), H (1s 1 ), B (2s 2 2p 1 ), Cu (3d 9.5 4s 1.5 ), Mg (3s 2 ), and Si (3s 2 3p 2 ). Convergence tests determined a plane-wave cutoff energy of 55 Ry and a Monkhorst–Pack k-point mesh of 9 × 9 × 9, ensuring total energy convergence within 1–2 meV/atom. Structural optimizations were carried out using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm with convergence thresholds of 1 × 10⁻ 6 eV/atom for energy and 1 × 10⁻ 3 eV/Å for forces. Phonon dispersion, mechanical properties, and optical responses were evaluated using the thermo_pw package integrated with Quantum ESPRESSO.