Description of Si-O bond breakage using pair-wise interatomic potentials under consideration of the whole crystal

We extend the McPherson model in a manner to capture the effect of the whole surrounding lattice on the silicon-oxygen bond-breakage energetics. It is shown that the Mie-Gruneisen potential with the constants used in the original version of the model is not suitable under the consideration of the whole crystal. Other empirical pair-wise interatomic potentials, namely TTAM and BKS have been tested for the analysis of the bond rupture energetics. It is shown that the secondary minimum corresponding to the transition of the Si atom from the 4-fold to the 3-fold coordinated position occurs in a different direction with a rather high activation energy (~6 eV). The tunneling of the Si ion between the primary and the secondary minima has been treated within the WKB approximation. We demonstrate that the contribution of neighboring SiO₄ tetrahedrons substantially decreases the breakage rate, making bond rupture by means of an electric field alone practically impossible. Therefore, the common action of an electric field and another contribution (bond weakening by hole capture, structural disorder and energy deposited by particles) is essential for Si-O bond-breakage.