Clusters of self-interstitial atoms formed in displacement cascades in metals irradiated with energetic particles played an important role in microstructure evolution under irradiation. They were studied in the face-centered cubic and body-centered cubic metals by atomic-scale computer simulation, and the results were presented here of a similar study in a hexagonal close-packed crystal. Static and dynamic properties of clusters of up to 30 self-interstitial atoms were studied by using a many-body Finnis-Sinclair type interatomic potential for Zr. The results showed a qualitative similarity of some properties of clusters to those for cubic metals. In particular, all clusters larger than 4 self-interstitial atoms exhibited fast thermally activated 1-dimensional glide in the hexagonal close-packed lattice. Due to the structure of the hexagonal close-packed lattice, this mechanism led to 2-dimensional mass transport in basal planes. Some clusters exhibited a behavior peculiar to the hexagonal close-packed structure, in that they could migrate 2-dimensionally in the basal plane. The jump frequency, activation energy, and correlation factors of clusters were estimated, and comparisons drawn between the behavior of self-interstitial atom clusters in different structures.

Mobility of Interstitial Clusters in Alpha-Zirconium. N.de Diego, Y.N.Osetsky, D.J.Bacon: Metallurgical and Materials Transactions A, 2002, 33[3A], 783-9