The I4 cluster model, which had been suggested to involve mainly self-interstitial clustering, was studied by using an ab initio pseudopotential method which was based upon local density-functional theory. All of the bonds were well-reconstructed, with relatively little bond distortion. The formation energy per self-interstitial was 1.5eV. This value was less than half of that of isolated self-interstitials, although it was larger than that of extended self-interstitial agglomerates such as {113} planar defects. The I4 cluster had no electronic states within the minimum band gap.

First-Principles Calculations of the Self-Interstitial Cluster I4 in Si M.Kohyama, S.Takeda: Physical Review B, 1999, 60[11], 8075-80