Diffusion of Atomic Oxygen in SiO 2
Density functional calculations using an \ensuremath{\alpha}-quartz supercell as a model silica host identify the peroxy linkage as the lowest energy configuration of atomic O in Si${\mathrm{O}}_{2}$, and find that its energy in this site and in interstitial molecular ${\mathrm{O}}_{2}$ are nearly equal. Using ab initio molecular dynamics modified to converge to a saddle point, the barrier for concerted exchange of the peroxy linkage is found to be 1.3 eV. While O is generally believed to diffuse in molecular form in Si${\mathrm{O}}_{2}$, measured diffusion activation energies are consistent with the peroxy exchange barrier.