THEORY OF TWOFOLD COORDINATED SILICON AND GERMANIUM ATOMS IN SOLID SILICON DIOXIDE

Computer simulation of twofold coordinated silicon and germanium atoms in solid silicon dioxide is performed in a cluster approach with various boundary conditions with the help of the quantum-chemical MO method MNDO. Optical absorption and luminescence in the twofold coordinated atoms are found to disagree with those of oxygen-deficient centres in solid silicon dioxide. It is concluded that the twofold coordinated atoms are no good models of oxygen-deficient centres.