Migration of Vacancies, He Interstitials and He-Vacancy Clusters at Grain Boundaries in alpha-Fe

Journal Article · Thu Apr 30 00:00:00 EDT 2009 · Journal of Nuclear Materials, 386:390-394

DOI:https://doi.org/10.1016/j.jnucmat.2008.12.159· OSTI ID:963570

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

he 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 sigma11<110> {323} and sigma3<110> {111} grain boundaries (GBs) in alpha-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 specific directions in both GBs: directly along close-packed rows in the sigma3 GB, and in zigzag paths within the sigma11 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. 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. This is comparable to the migration energy for a He-divacancy cluster in bulk alpha-Fe.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 963570
• Report Number(s): PNNL-SA-64135; JNUMAM; AT6020100; TRN: US200918%%330
• Journal Information: Journal of Nuclear Materials, 386:390-394, Vol. 386; ISSN 0022-3115
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
IRON
HELIUM
ACTIVATION ENERGY
DIFFUSION
GRAIN BOUNDARIES
INTERSTITIALS
VACANCIES
MASS TRANSFER
SIMULATION
Migration of He defects
He-Vacancy clusters
Grain Boundaries
Computer Simulation