Diffusion coefficient in crystals with multiple jump frequencies

A general method is described for the derivation of the diffusion coefficient in a crystal lattice in terms of jump frequencies where more than one jump frequency is involved. The method is applicable mainly to interstitial-type diffusion. As examples of the application of the method, the diffusion coefficients are derived for an interstitial impurity occupying both tetrahedral and octahedral interstices in h.c.p. or b.c.c. lattices, and for a ‘diplon’ in the f.c.c. lattice.