CLUSTER MODELING OF THE NEUTRAL OXYGEN VACANCY IN PURE SILICON DIOXIDE

The main results of the computer simulation of the oxygen vacancy in pure silicon dioxide are presented. The semi-empirical method, MNDO from the MOPAC package, is used. Silicon dioxide is simulated by molecular clusters of different sizes and structures. Calculated positions of the absorption and luminescence bands of the neutral oxygen vacancy are in satisfactory agreement with those of the oxygen-deficient center observed in pure silicon dioxide. The absorption and luminescence bands of the vacancy correspond to the dipole allowed one-electron transitions between two localized states with the levels in the energy gap of SiO2. The lower level is doubly occupied; the upper one is empty, resulting from the bonding and antibonding combination of sp orbitals of two silicon atoms adjacent to the vacant site, respectively.