It was noted that recent molecular dynamics simulations had shown that clusters which consisted of up to a few tens of self-interstitial atoms were highly mobile along close-packed crystallographic directions. The results of molecular dynamics modelling of the thermally-activated motion of clusters of 3, 9 and 17 self-interstitial atoms in α-Fe at 90 to 1400K were analyzed here. A correlation between the motion of the centre of mass of a cluster, and the individual jumps of its constituent self-interstitial atoms, was revealed. It was found that the self-interstitial atoms in a cluster jumped almost independently, and that their jump frequency depended upon the number of self-interstitial atoms in the cluster. This led to a simple relationship between the jump frequency of a cluster and the number of self-interstitial atoms which it comprised. It was shown that such clusters only exhibited an effectively random walk, with a correlation factor of unity, when the jump-length which defined diffusion was taken to be 3b to 4b; where b was the magnitude of the vector, ½<111>.

Mechanism of One-Dimensional Glide of Self-Interstitial Atom Clusters in α-Iron. A.V.Barashev, Y.N.Osetsky, D.J.Bacon: Philosophical Magazine A, 2000, 80[11], 2709-20