The First-principles Study of Hydrogen Adsorption and Diffusion Processes on Zirconium Surfaces and in Bulk

The hydrogen adsorption and diffusion mechanisms at zirconium surfaces and bulk phases were systematically investigated through first-principles calculations to address unresolved questions regarding atomic-scale hydrogen interactions. The study focused on four critical stages of hydrogen incorporation: molecular dissociation, surface adsorption, interfacial diffusion/penetration, and bulk-phase diffusion. Energy barriers along specific diffusion pathways were calculated using the climbing-image nudged elastic band (CI-NEB) method, with temperature-dependent diffusion coefficients derived for each pathway. Computational results revealed a dissociation barrier of 0.07 eV for hydrogen molecules at surface sites, followed by preferential adsorption of atomic hydrogen at hexagonal close-packed (hcp) sites. Subsequent energy barriers were quantified as 0.31 eV for hcp → face-centered cubic (fcc) surface diffusion, 0.85 eV for fcc surface → subsurface octahedral site penetration, and 0.43 eV for tetrahedral → octahedral site transitions in bulk zirconium. Comparative analysis identified the surface-to-subsurface transition as the rate-limiting step governing hydrogen absorption kinetics. This study provided atomic-scale insights into hydrogen permeation mechanisms in zirconium-based systems, serving as a theoretical foundation for optimizing getter materials and mitigating hydrogen embrittlement in nuclear reactor cladding applications.