A di-interstitial model was proposed for the P6 center which was commonly observed in ion-implanted material. The di-interstitial structure, and the transition paths between various defect orientations, could explain the thermally activated transition of the P6 center from low-temperature C1h to room-temperature D2d symmetry. The activation energy for defect reorientation, as deduced from ab initio calculations, was 0.5eV. This value agreed with experimental observations. The di-interstitial model established a link between point defects and {311} defects, and supported the concept of growth via interstitial nucleation.

Thermally Activated Reorientation of Di-Interstitial Defects in Silicon J.Kim, F.Kirchhoff, W.G.Aulbur, J.W.Wilkins, F.S.Khan, G.Kresse: Physical Review Letters, 1999, 83[10], 1990-3