“…A precisely similar approach to that for self-diffusion can be followed so that for a vacancy or interstitialcy mechanism, or indeed a mixture of the two, the resultant impurity diffusivity, Dimp, is quite generally expressed by [8] where D x , Dr', and Dr' now refer to the impurity diffusivities associated with the particular charge states of the native defect under intrinsic conditions. Whereas in self-diffusion th.e correlation factor is a constant for a given diffusion mechanism (i.e.independent of defect charge state), the correlation factors contained in each term on the rtight-hand side of (2.10) will in general depend on the charge state even for the stme diffusion mechanism.…”