The annihilation of a tetrahedral interstitial by a vacancy was studied by using molecular dynamics and the Goodwin-Skinner-Pettifor tight-binding model. The annihilation process was dominated, at 1473 and 1173K, by the movement of the faster-diffusing vacancy. When the vacancy moved to a nearest-neighbour position relative to the interstitial, annihilation became inevitable. As the initial distance between the T-interstitial and the vacancy increased, the number of pathways via which annihilation could occur increased accordingly. Fast and slow annihilation pathways were identified. The process was found to be highly stochastic; requiring multiple simulations in order to provide adequate statistics. The system size was not a factor which affected the results. The capture radius, within which annihilation was assured, was found to be between 0.5 and 0.6nm at 1473K. However, it was clear from the orientation dependence of the results that a spherically symmetrical view of the capture radius was perhaps inappropriate. A limited investigation of annihilation, between a (110) split interstitial and a vacancy, confirmed the prediction that the formation of a double-vacancy plus double-interstitial configuration (a so-called bond-defect) occurred in some, but not all, cases as part of the annihilation mechanism.

Tight-Binding Molecular Dynamics Study of Vacancy-Interstitial Annihilation in Silicon. M.T.Zawadzki, W.Luo, P.Clancy: Physical Review B, 2001, 63[20], 205205 (14pp)