Differences in He nucleation mechanisms between Cu and Cu/Nb interfaces: first-principles calculations

In this work, first-principles calculations were employed to investigate the stability of He clusters and vacancy-He interactions in Cu and Cu/Nb interfaces, revealing microscopic mechanisms for suppression of He bubbles growth in Cu/Nb composites. He atoms tend to aggregate at the interface rather than in the bulk. Binding energy results show that the Cu/Nb interface lowers the stability of He clusters by inhibiting the He-driven self-trapping effect and weakens the ability of vacancy trapping He atoms, hindering the formation of large size He clusters and bubble nucleation. Ab initio molecular dynamics (AIMD) calculations demonstrated that the Cu/Nb interface hinders the diffusion of He, and the variation of diffusion trajectory at the interface is negligible with increase of temperature, which contrasts sharply with the thermally enhanced diffusion of bulk Cu. This work deepens the understanding of nucleation mechanisms of He in radiation-resistant composites.