EXTENDED MODEL OF THE CHANNEL DIFFUSIVITY IN THE RUTILE STRUCTURE

A model describing the diffusivity of a highly diluted and randomly di stributed substitutional cationic impurity via the open and almost emp ty (001) channels in the rutile structure has been developed recently. The above model is based upon the assumption that the insignificant f raction of the impurities resides in the channels. An extended model i s developed that allows for a significant fraction of the impurities t o stay within channels, and it is used to evaluate emission Mossbauer spectra originating from the diffusing impurities embedded in single-c rystalline samples. Final results are shown for the 14.4-keV Mossbauer line in Co-57(Fe). It is shown that spectral line positions depend up on the wave-vector transfer to the system, and that the data are sensi tive to the fraction of both parent and daughter impurities residing i n the channels.