An analysis was made of the defect formation energies for diffusion via home and foreign sub-lattices. The home sub-lattice mechanism was the preferred one for both Si and Mo. Tracer correlation factors for Si and Mo diffusion via sub-lattice vacancies in the respective sub-lattices of the tetragonal C11b structure of the disilicide were calculated by using direct Monte Carlo simulation. Correlation factors for Si diffusion on its sub-lattice were compared with literature values that had been calculated using a more complicated Monte Carlo method based upon the matrix approach. It was shown that there was no need for this complicated approach, and that the direct Monte Carlo technique gave highly accurate correlation factors. The 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 0.40eV (over 55%) of the migration energy of the corresponding Si diffusivity. Two possible jump rates for Si diffusion were separately estimated. The Mo diffusion correlation factors were calculated using the direct Monte Carlo technique.

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