First-principles methods were used to investigate self-interstitials and their aggregates. It was recalled that the attribution of the spin-1 R2 electron paramagnetic resonance center to the single interstitial had been questioned because of a small observed fine-structure term. The spin-spin interaction tensor was calculated for the interstitial defects, I1<001>, I2NN and I3, and was compared with experimentally determined D tensors. The results supported previous attributions of the single and di-interstitials, and permitted the conclusive identification of a newly observed electron paramagnetic resonance center, O3, as being I3. This in turn suggested a low-energy structure for I4, and a generic model for an extended defect (platelet). Several multi-interstitial defects were found to have various structural forms, which could coexist. It was proposed that a different form of the charged I2 defect gave rise to the 3H optical peak. Several structures for the platelet were considered, and it was found that the lowest-energy model was consistent with microscopic and infra-red studies.

Self-Interstitial Aggregation in Diamond. J.P.Goss, B.J.Coomer, R.Jones, T.D.Shaw, P.R.Briddon, M.Rayson, S.Öberg: Physical Review B, 2001, 63[19], 195208 (14pp