It was recalled that the formation of prismatic dislocation loops was an important factor leading to the radiation damage of metals. However, their formation mechanism and the size of the smallest stable loop had remained unclear. Electronic structure calculations, using millions of atoms, were used here to address this problem for Al. The results showed that there was a cascade of larger and larger vacancy clusters of smaller and smaller energy. The results also showed that a 7- vacancy cluster on the (111) plane could collapse into a stable prismatic loop. This supported the long-standing hypothesis that vacancy-clustering led to a prismatic loop, and that these loops could be stable at extremely small sizes. Finally, the results showed that it was important to perform calculations by using realistic concentrations (computational cell-size) in order to obtain physically meaningful results.

Vacancy Clustering and Prismatic Dislocation Loop Formation in Aluminium. V.Gavini: Physical Review B, 2007, 76[18], 180101 (4pp)