Mobility of interstitial clusters in alpha-zirconium

Clusters of self-interstitial atoms (SIAs) formed in displacement cascades in metals irradiated with energetic particles play an important role in microstructure evolution under irradiation. They have been studied in the fcc and bcc metals by atomic-scale computer simulation, and in this article, we present the results of a similar study in a hexagonal close-packed (hcp) crystal. Static and dynamic properties of clusters of up to 30 SIAs were studied using a many-body Finnis-Sinclair type interatomic potential for Zr. The results show a qualitative similarity of some properties of clusters to those for cubic metals. In particular, all clusters larger than four SIAs exhibit fast thermally activated one-dimensional (1-D) glide, which is in a 〈11 $$\bar 2$$ 0〉 direction in the hcp lattice. Due to the structure of the hcp lattice, this mechanism leads to two-dimensional mass transport in basal planes. Some clusters exhibit behavior peculiar to the hcp structure, for they can migrate two-dimensionally (2-D) in the basal plane. The jump frequency, activation energy, and correlation factors of clusters have been estimated, and comparisons drawn between the behavior of SIA clusters in different structures.