On the structure and mobility of point defect clusters in alpha-zirconium: a comparison for two interatomic potential models

A recent interatomic potential for alpha-zirconium (Zr) is used to investigate the atomic configuration and motion of point defect clusters. The structure of the single self-interstitial atom (SIA) has a strong influence on the properties of small clusters containing up to six interstitials. For a given number of defects in this size range, several configurations exist with similar formation energy but different dynamic properties, i.e. they may be sessile or glissile. The movement of small clusters is three-dimensional and involves combinations of the different configurations. As cluster size increases, the influence of the configuration of the stable single SIA vanishes and the interstitials orientate to achieve near-perfect crystal structure inside the cluster and a dislocation-core arrangement at the periphery. Movement of clusters larger than 12 SIAs is one-dimensional along the direction of the Burgers vector. The stable configurations of vacancy clusters are also studied. The results are compared with those predicted with a model based on an earlier interatomic potential