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Title: Energetic Study of Helium Cluster Nucleation and Growth in 14YWT through First Principles

First principles calculations have been performed to energetically investigate the helium cluster nucleation, formation and growth behavior in the nano-structured ferritic alloy 14YWT. The helium displays strong affinity to the oxygen:vacancy (O:Vac) pair. By investigating various local environments of the vacancy, we find that the energy cost for He cluster growth increases with the appearance of solutes in the reference unit. He atom tends to join the He cluster in the directions away from the solute atoms. Meanwhile, the He cluster tends to expand in the directions away from the solute atoms. A growth criterion is proposed based on the elastic instability strain of the perfect iron lattice in order to determine the maximum number of He atoms at the vacancy site. We find that up to seven He atoms can be trapped at a single vacancy. However, it is reduced to five if the vacancy is pre-occupied by an oxygen atom. Furthermore, the solute atoms within nanoclusters, such as Ti and Y, will greatly limit the growth of the He cluster. A migration energy barrier study is performed to discuss the reduced mobility of the He atom/He cluster in 14YWT.
 [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. Clemson University
  2. ORNL
  3. Argonne National Laboratory (ANL)
  4. Shanghai Jiao Tong University, China
Publication Date:
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Resource Relation:
Conference: TMS 2015: 144th Annual Meeting and Exhibition, Orlando, FL, USA, 20150315, 20150319
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
Work for Others (WFO)
Country of Publication:
United States