Diffusion data for both principal directions of silicon and molybdenum as well as germanium were briefly summarised. Analysis was performed of the defect formation energies (available from previous ab initio calculations and experimental measurements) for diffusion mechanisms via home and foreign sub-lattices. The home sub-lattice mechanism was shown to be the preferred one for both silicon and molybdenum. Tracer correlation factors for silicon and molybdenum diffusion via sub-lattice vacancies in the respective sub-lattices of the tetragonal C11b structure of molybdenum disilicide were calculated by a direct Monte Carlo simulation technique. Correlation factors for Si diffusion on its sub-lattice were compared with literature values that were calculated using a more complicated Monte Carlo method based on the matrix approach. It was shown that there was no need for this complicated approach and that the direct Monte Carlo simulation technique gives highly accurate correlation factors. Correlation factors and anisotropy ratios of vacancy-mediated diffusion in both sub-lattices were deduced and compared with experimental data. Tracer correlation in the tetragonal direction was shown to contribute 0.40 eV (i.e. over 55%) of the migration energy of the corresponding Si diffusivity. Two possible jump rates for Si diffusion were separately estimated. Mo diffusion correlation factors were calculated using the direct Monte Carlo technique. A comparison with experiment was made and the ratio of two possible jump rates was also estimated.

Diffusion Correlation Effects of Molybdenum and Silicon in Molybdenum Disilicide. I.V.Belova, H.Mehrer, G.E.Murch: Philosophical Magazine, 2011, 91[28], 3727-43