The motion and clustering of vacancies and interstitials in silicon were simulated. The diffusion coefficients of isolated defects were deduced from atomic displacements in simulations performed over a wide range of temperatures. The results indicated an apparent migration energy barrier of 0.43eV for vacancies and 0.9eV for interstitials. The diffusion coefficients were between 10-6 and 10-5cm2/s at 800C, and were in approximate agreement with first-principles calculations, but were many orders of magnitude larger than the most direct experimental measurements. Simulations involving high concentrations of defects showed that like defects aggregated into stable clusters, and that individual defects were bound to these clusters with energies in the range of 0.6 to 2.3eV. Defect clusters had mobilities which could differ substantially from those of the individual defects. The di-interstitial had a markedly smaller diffusion barrier (0.2eV), while the tri-interstitial had a mobility which was so small that it was difficult to measure accurately by molecular dynamics simulation.

Diffusion and Interactions of Point Defects in Silicon: Molecular Dynamics Simulations. Gilmer, G.H., Diaz de la Rubia, T., Stock, D.M., Jaraiz, M.: Nuclear Instruments and Methods in Physics Research B, 1995, 102[1-4], 247-55