Stability of Si-interstitial defects: from point to extended defects

Trends in the growth of extended interstitial defects are extracted from extensive tight-binding and ab inito local density approximation simulations. With an increasing number of interstitials, the stable defect shape evolves from compact to chainlike to rodlike. The rodlike 311 defect, formed from (011) interstitial chains, is stabilized as it grows, elongating in the chain direction. Accurate parametrization of the defect-formation energy on the number of interstitials and interstitial chains, together with the anisotropy of the interstitial capture radius, enables macroscopic defect-growth simulations.