Diffusion Coefficient in an Ordered Binary Alloy

The isotope diffusion coefficient of one of the components in a binary ordered alloy is derived for the vacancy mechanism by the path probability method. By introducing the concept of the transposed lattice and making full use of the symmetry of the system, the derivation is made transparent and simpler than the treatment reported previously. The new derivation leads quite naturally to decomposition of the correlation factor into two components related to the two sublattices; the decomposition leads to a detailed interpretation of the correlation factor. The vacancy availability factor and the effective jump frequency factor are defined and their importance in the diffusion in the ordered phase is pointed out.