First-Principles Studies of Hydrogen Diffusion Mechanisms in FCC Metals: Al and Cu as Case Studies*

Understanding hydrogen's behavior in metals holds immense significance for various industrial and energy applications, including hydrogen storage and embrittlement mitigation. In this study, we performed first principles calculations and molecular dynamics simulations to understand the diffusion process of hydrogen in FCC aluminum (Al) and copper (Cu) systems. Nudged elastic band calculations were employed to determine the pathways of hydrogen within both the Al and Cu systems. It is shown that for the most energetically probable pathway between stable H sites, Cu has a larger energy barrier with respect to Al resulting in a slower H diffusion. These findings were verified by calculating the diffusion coefficient of H for each system by employing molecular dynamic simulations. Calculated diffusion coefficients are in very good agreement with experimental measurements.