Migration of Positively Charged Defects in (alpha)-Quartz

摘要

We apply a newly developed quantum-mechanics/ molecular-mechanics (QM/MM)scheme to-quartz. We simulate the transition mechanism and compute the potential energy and free energy surface for the puckering of the symmetric charged oxygen vacancy and the formation of the E(1) center. By overcoming low energy barriers this puckering mechanism can be reiterated allowing the drift of the positive charge localized on an over-coordinated oxygen atom. This process enhances the stability of theE(1) center and can be regarded as an important channel of structural reorganization of oxygen deficient silica in the presence of strong polarizing electric fields.