Diffusion of atomic oxygen in SiO2

Density functional calculations using an alpha-quartz supercell as a model silica host identify the peroxy linkage as the lowest energy configuration of atomic O in SiO2, and find that its energy in this site and in interstitial molecular 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 SiO2, measured diffusion activation energies are consistent with the peroxy exchange barrier. [S0031-9007(98)07404-3].