Abstract
Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. However, the precise role of the interfaces in modifying defect behavior is unclear. Using long-time simulations methods, we determine the mobility of defects and defect clusters at grain boundaries in Cu. We find that mobilities vary significantly with boundary structure and cluster size, with larger clusters exhibiting reduced mobility, and that interface sink efficiency depends on the kinetics of defects within the interface via the in-boundary annihilation rate of defects. Thus, sink efficiency is a strong function of defect mobility, which depends on boundary structure, a property that evolves with time. Further, defect mobility at boundaries can be slower than in the bulk, which has general implications for the properties of polycrystalline materials. Finally, we correlate defect energetics with the volumes of atomic sites at the boundary.
Highlights
Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance
We find that mobilities vary significantly with boundary structure and cluster size, with larger clusters exhibiting reduced mobility, and that interface sink efficiency depends on the kinetics of defects within the interface via the in-boundary annihilation rate of defects
Our results indicate that as both the defect cluster size increases and the character of grain boundary (GB) becomes more complex, defect mobility is reduced such that their mobility becomes slower than in bulk Cu
Summary
Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. In spite of this large body of work, there are still important questions that remain unanswered, relating to the interplay between grain boundaries and defects produced in extreme environments In such conditions, the defect content at the boundaries can be significantly higher than at equilibrium such that defects begin to interact and cluster. We found that damaged GBs, modeled as boundaries with excess defect content, would have stronger www.nature.com/scientificreports interactions with residual defects in the bulk of the material that are dramatically different than their pristine counterparts This led us to conclude that the sink efficiencies of interfaces will not be a static quantity but will evolve in a complex manner during irradiation as the steady state concentration of defects within the GB will depend on both boundary character and irradiation conditions[19]. This demonstrates a direct correlation between interface structure, defect mobility within the interface, and sink efficiency of the interface
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