Atomic-scale computer simulations were used to study the thermally activated atomic transport of self-interstitial atoms in the form of planar clusters in α-Fe. It was recalled that there was strong evidence that such clusters were commonly formed in metals during irradiation with high-energy particles, and played an important role in the accumulation and distribution of the surviving defects. An extensive study of the mobility of self-interstitial atom clusters which contained 2 to 331 interstitials was carried out by using molecular dynamics simulations techniques at 180 to 1200K. The results obtained showed that clusters which were larger than 3 to 4 self-interstitial atoms in size were 1-dimensionally mobile. Large clusters, with more than 300 self-interstitial atoms, exhibited a significantly reduced mobility. An attempt was made to describe the mobility of self-interstitial atoms clusters within the 1-dimensional diffusion approximation. The effective cluster migration energy for 1-dimensional diffusion - as estimated from the jump frequency of the cluster center-of-mass - was found to be independent of the number of self-interstitial atoms in the cluster; although the cluster jump frequency decreased with increasing cluster size.
One-Dimensional Atomic Transport by Clusters of Self-Interstitial Atoms in Iron and Copper. Y.N.Osetsky, D.J.Bacon, A.Serra, B.N.Singh, S.I.Golubov: Philosophical Magazine, 2003, 83, 61-91