Effect of hydrogen atom concentration on hydrogen migration and bubble evolution in bcc iron

The effect of the concentration of hydrogen (H) atoms on the hydrogen diffusion and evolution of hydrogen bubbles in body-centered cubic iron was investigated using molecular statics and molecular dynamics methods. The simulation results indicate that the local accumulation of H atoms can significantly influence their migration. Compared to the isolated H in a perfect lattice, the H atoms in a high-concentration H-cluster are trapped. After collecting a sufficient amount of hydrogen atoms, the H-vacancy cluster will push out one hydrogen atom instead of a self-interstitial atom, which indicates that loop-punching will not dominate the H-bubble growth in bcc iron. These results will provide a new understanding for the hydrogen-induced radiation damages in nuclear materials.