The atomic and electronic structure of interstitial O in bulk Si was studied using a semi-empirical Hartree--Fock technique. The calculations were performed in real space on a H-terminated cluster in combination with a new parameterization of O within the framework of the modified neglect of diatomic overlap technique. It was found that the results for the Si cluster were in good agreement with experiment as well as with the results of ab initio calculations. Moreover, the various charge states of the O were analyzed. It was found that interstitial O in both neutral and double negative charge state forms a stable configuration but the single negative state forms an instable configuration with a strong level in the band gap at Ev +0.55eV.

Oxygen Defect in Silicon Studied by Semi-Empirical Calculations. P.Ballo, L.Harmatha, D.Donoval: Computational Materials Science, 2008, 42[2], 380-4