In photoluminescence experiments, the DII center exhibited strong C–like vibrational modes above the highest bulk phonon mode. Ab initio density-functional theory calculations were made of the localized vibrational modes of defects with C–C bonds. Among these defects, only the C split-interstitial plus antisite complex was found to exhibit a localized vibrational mode spectrum that was compatible with that of the DII center. The formation energy of this complex was comparable to the formation energy of the most abundant interstitial defects: the C split-interstitial and the C–Si split interstitial. A high binding energy (3.6eV or more) was found.

Interstitials in SiC - a Model for the DII Center. A.Mattausch, M.Bockstedte, O.Pankratov: Physica B, 2001, 308-310, 656-9