The motion and clustering of vacancies and interstitials were simulated by using molecular dynamics methods. The diffusion coefficients of isolated defects were estimated from the atomic displacements in simulations which were performed over a wide range of temperatures. The results yielded an apparent migration energy of 0.43eV for vacancies and 0.9eV for interstitials. The diffusion coefficients were between 10-6 and 10-5cm2/s at 800C, and agreed approximately with first-principles calculations, but were many orders of magnitude higher than the most direct experimental values. Simulations of high concentrations of defects showed that like defects aggregated into stable clusters, and that individual defects were bound to these clusters with energies ranging from 0.6 to 1.3eV. The defect clusters had mobilities which could be appreciably different to those of individual defects. The di-interstitial had a much smaller diffusion energy (about 0.2eV), whereas the tri-interstitial had a mobility which was so small that it was difficult to measure accurately in molecular dynamics simulations.

G.H.Gilmer, T.Diaz de la Rubia, D.M.Stock, M.Jaraiz: Nuclear Instruments and Methods in Physics Research B, 1995, 102[1-4], 247-55