The dimer method was used to search for possible transition states of interstitials and small interstitial clusters in α-Fe. The method used only the first derivatives of the
potential energy to find saddle points, without knowledge of the final state of the transition. The possible transition states were studied as a function of interstitial cluster size, and the lowest energy barriers corresponded to defect migration along <111> directions. It was considered whether migrating interstitial clusters could thermally change their direction, and the activation energies and corresponding mechanisms for changing the direction of these clusters were determined.

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