π-bonded model of an oxygen-vacancy center in SiO2

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Abstract
Tight‐binding total energy calculations of the two possible states of the neutral oxygen‐vacancy center in SiO2 have been performed within the bond orbital approximation. It has been shown that the lowest energy state is realized by a transfer of one electron from a nonbonding p oxygen orbital (next to the vacancy) into an opposite silicon dangling hybrid, and then by the formation of a π bond between the remaining oxygen p electron and the nearest silicon dangling hybrid. The new π‐bonded model of the oxygen‐vacancy center is discussed and the results obtained are compared with experimental data. The most important aspect of this work is the demonstration that for defects in SiO2, the π interactions are very important and should not be neglected in describing the physics of many problems in SiO2.