Dual Role of Hydrogen Effect on Surface Dislocation Nucleation in Nickel

Abstract Hydrogen embrittlement poses a significant challenge to hydrogen transportation and storage in advancing the hydrogen economy. Despite extensive research, uncertainty regarding how hydrogen affects dislocation nucleation, owing to the lack of quantitative evidence, hinders our understanding of hydrogen embrittlement. In this study, we demonstrate that hydrogen atoms influence surface dislocation nucleation differently depending on their locations: hydrogen at the surface inhibits nucleation, while hydrogen in the bulk promotes it. This dual behavior is attributed to differences in hydrogen binding energies at various sites, a phenomenon further validated through nudged elastic band calculations and transition state theory. Additionally, we propose a modified nucleation rate that incorporates thermal expansion effects, which aligns closely with results from molecular dynamics simulations. These findings at the individual dislocation level offer promising guidance, suggesting that strategies such as suppressing hydrogen accumulation at the surface might effectively mitigate hydrogen embrittlement issues.