It was recalled that energetic primary recoil atoms from ion implantation or fast neutron irradiation produced isolated point defects and clusters of vacancies and interstitials. The migration energies and mechanisms of these defects were required for the successful multi-scale modeling of microstructural evolution during ion-implantation, annealing or during long-term irradiation. The dimer method was used to search for possible transition states of interstitials and small interstitial clusters in SiC and α-Fe. The method used only the first derivatives of the potential energy to locate saddle points. No knowledge of the final state of the transition was needed. In SiC, the possible migration pathway for the C interstitial was found to consist of the first-nearest neighbor jump via a Si site or second-nearest neighbor jump; but the relative probability for the second-nearest neighbor jump was very low.

Finding Possible Transition States of Defects in Silicon-Carbide and Alpha-Iron using the Dimer Method. F.Gao, G.Henkelman, W.J.Weber, L.R.Corrales, H.Jónsson: Nuclear Instruments and Methods in Physics Research B, 2003, 202, 1-7