Identification of the tetra-interstitial in silicon

First-principles computational methods are employed to investigate the stru ctural, vibrational, optical and electronic properties of the self-intersti tial aggregate, I-4 in silicon. We find the defect to be electrically activ e and identify it with the B3 EPR centre. We also show that its properties are consistent with DLTS and optical spectra observed following implantatio n of silicon.