Small clusters of vacancies were introduced into a crystal of 4000 atoms at randomly selected positions. Computer simulations were carried out using an isotropic potential and embedded atom methods for 1200, 1500, 1600 and 1700K. Forty single vacancies were observed to cluster at 1700K after a molecular dynamics run of 100ps, while 4 single vacancies were not observed after 600ps. A further run was required for vacancies to agglomerate. Triangular tri-vacancies also grew into a larger cluster from 2 tri-vacancies which were initially closer than other tri-vacancies. When 4 clusters of triangular 15-vacancies were introduced, they at first relaxed into a stacking-fault tetrahedron. Changes in cluster structure played an important role in agglomeration. No agglomeration occurred at low temperatures.

Computer Simulation of the Clustering of Small Vacancies in Nickel. R.Nishiguchi, Y.Shimomura: Computational Materials Science, 1999, 14[1-4], 91-6