The geometrical and electronic structures of doubly positively charged oxygen

vacancies in a-SiO2 were calculated. Four types of relaxed configuration were

found in the amorphous matrix; corresponding to puckered and unpuckerd

configurations of Si atoms of the vacancy. The predicted optical absorption

strongly depended upon the atomic configuration of a particular center, and the

transition energies ranged from 4.5 to 6.5eV.

Doubly Positively Charged Oxygen Vacancies in Silica Glass. A.V.Kimmel,

A.L.Shluger: Journal of Non-Crystalline Solids, 2009, 355[18-21], 1103-6