A study was made of self-interstitial cluster migration properties, such as the dimensionality of the motion and the activation energy barrier, as functions of the cluster size using molecular-dynamics simulations of body-centered cubic Fe. The atomic interactions were described by using a new potential; chosen so as to reproduce self-interstitial atom configuration energies which were in close agreement with the results of ab initio calculations. It was shown that this potential provided a dynamic migration energy for the single self-interstitial atom in agreement with the experimental value. It was also shown that, in the case of clusters formed by up to 5 self-interstitial atoms, the migration energy decreased with increasing cluster size, but remained higher than was previously believed. This was a result of the change, in the migration mechanism of these small clusters, from purely 3-dimensional to preferentially 1-dimensional and of the fact that these clusters took on various configurations during migration; including anomalous ones. While the concept of fast 1-dimensional diffusion of large self-interstitial atom clusters remained valid, the obtained results suggested a needed revision of both the rapidity and the dimensionality of the motion of small interstitial clusters.

Dimensionality of Interstitial Cluster Motion in BCC-Fe. D.A.Terentyev, L.Malerba, M.Hou: Physical Review B, 2007, 75[10], 104108 (13pp)