Migration of vacancies, HE insterstitials and HE-vacancy clusters at grain boundaries in α-FE

Book · Sat Mar 01 04:00:00 EST 2008

OSTI ID:1328077

Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.

The dimer method for searching transition states has been used to systematically study possible migration paths of vacancies, He interstitials and He-vacancy (He/V) clusters at Σ11<110> {323} and Σ3<110> {111} grain boundaries (GBs) in α-Fe. Vacancies trapped at the GBs diffuse along the GBs with migration energies much less than that within the perfect crystal. Long-time dynamics simulations of diffusion pathways reveal that vacancies migrate one-dimensionally along the close-packed rows in the Σ3 GB, and one-dimensionally in zigzag paths within the Σ11 GB. Also, dimer saddle point searches show that He interstitials can diffuse along the GBs with migration energies of 0.4-0.5 eV, similar to those of individual vacancies at the GBs, and the corresponding mechanisms are determined. Finally, the rate-controlling activation energy for migration of a He-divacancy cluster in the GBs determined using the dimer method is about 0.9 eV, which is comparable to the migration energy for a He-divacancy cluster in bulk α-Fe.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1328077
• Report Number(s): PNNL-SA--58951; DOE/ER--313/43; AT2030110
• Country of Publication: United States
• Language: English