Analyzing the synergistic impact of hydrogen and structural defects on nickel's mechanical and diffusion characteristics

Abstract

This comprehensive study investigates the interplay between hydrogen atoms and structural defects, including vacancies and self-interstitial atom defects (SIAs), and their combined impact on hydrogen diffusion and mechanical properties in nickel through molecular dynamics simulations. The results indicate that the diffusion coefficient of hydrogen in nickel in the temperature range of 400 K to 1000 K follows the Arrhenius law, yielding an activation energy of 0.424 eV and a diffusion coefficient pre-exponential factor of 8.185 × 10⁻⁸ m² s⁻¹, aligning well with experimental values. The findings also highlight the intricate link between hydrogen diffusion in nickel, defect concentrations, and temperature. Therefore, selecting an appropriate temperature range for studying the system is crucial to minimize quantum effects on hydrogen diffusion and obtain more accurate diffusion coefficient estimates. Our outcomes indicate that despite promoting hydrogen diffusion by SIAs, the existence of vacancies in the system impedes the migration of hydrogen atoms in nickel, thereby reducing diffusivity. The impact of varying concentrations of vacancies, SIAs, and hydrogen in Ni–H–defect systems was examined. It can be inferred that the diffusion coefficient of hydrogen in nickel is strongly influenced not only by the temperature range studied, but also by the type and concentration of structural defects, the concentration of hydrogen atoms, and even the ratio of the hydrogen concentration to the defect concentration (H/defect) in the system. The study also explored how nickel behaves mechanically when exposed to both hydrogen atoms and vacancies or SIAs, revealing a significant influence on its mechanical properties.