Theoretical modeling of O diffusivity in crystalline material at normal and high hydrostatic pressures was carried out by using molecular mechanics, semi-empirical and ab initio methods. It was established that the diffusion of an interstitial O atom (Oi) was controlled by the optimum configuration of three Si atoms nearest to Oi. The calculated values of the activation energy (2.59eV) and pre-exponential factor (0.28cm2/s) were in good agreement with experimental ones and, for the first time, described perfectly an experimental dependence of the Oi diffusion constant at 350 to 1200C. Hydrostatic pressures of up to 80kbar resulted in a linear decrease in the diffusion barrier (−4.38 x 10−3eV/kbar). The calculated pressure dependence of Oi diffusivity agreed well with the pressure-enhanced initial growth of O-related thermal donors.

Effect of Pressure on Oxygen Diffusion Jump in Si - Quantum-Chemical Simulations. V.Gusakov, L.Murin: Physica B, 2003, 340-342, 773-6