A quantum potential-barrier crossing model was used to explain the apparent deviation, from Arrhenius behavior, of O diffusion. In this model, an harmonically localized O-atom annihilated a metal-lattice phonon at the Debye frequency in order to gain enough energy to cross the potential barrier which separated it from a neighboring site. Taking 225K to be the Debye temperature of Ag, the model parameters were fitted to experimental data. This yielded values of 0.62eV and 76K for the height of the barrier and for the Einstein temperature of the O atom, respectively. A slightly concave-down shape of the Arrhenius plot was attributed to the fact that the Einstein temperature was less than two-thirds of the Debye temperature.

Diffusion of Oxygen in Silver. J.K.Baird, T.R.King, C.Stein: Journal of the Physics and Chemistry of Solids, 1999, 60[7], 891-4