Calculations concerning point-defect clusters were performed by using a static simulation technique, together with a many-body potential. The results were then compared with available experimental observations for hexagonal close-packed  metals with c/a ratios which were below the ideal value. It was found that both mono-vacancies and di-vacancies underwent an anisotropic migration (with almost the same activation energy) which corresponded to that observed in stage-IV recovery. Small vacancy clusters were found to favor 3-dimensional agglomerates. Small clusters of interstitials were shown to grow, on the basal plane, in forms which were based upon the octahedral point defect; although the most stable single interstitial was the non-basal crowdion. Large single-layer and double-layer interstitial clusters were suggested to be the embryos of experimentally observed dislocation loops.

A.G.Mikhin, N.De Diego, D.J.Bacon: Philosophical Magazine A, 1997, 75[4], 1153-70