Si-O bond-breakage energetics under consideration of the whole crystal

We extend the McPherson model for Si-O bond-breakage energetics, which considers only a single SiO4 tetrahedron, in a way to capture the effect of the whole crystal. No ledge in the direction assumed in the McPherson model was revealed. Instead, potential profiles feature a saddle point in a different direction. The activation energy for bond-breakage is found to be rather high (~ 6 eV). This suggests that the interaction with the electric field alone is not sufficient for bond rupture. The breakage rate calculated for a bond weakened by hole capture is comparable to that of the McPherson model. We conclude that only the common action of an electric field and other factors (structural disorder and/or energy delivered by particles, e.g. hot carriers) can result in bond-breakage.