Many diffusion systems present an anomalous fast diffusion (e.g. noble metals in Pb), which could be interpreted in terms of interstitial-substitutional exchange. Here, the dissociative variant of this model, where the exchange between interstitial and substitutional configurations took place with the interplay of vacancies, was simulated by using the Monte Carlo method, which permitted the avoidance of the drastic simplifications used to solve analytically the set of reaction-diffusion equations that described this model. The interstitial-vacancy pair (I-V), where the binding energy was considered up to second-nearest neighbours, was considered. The results showed that the penetration profiles changed their shape from a 2- to a 3-stage profiles, depending upon the magnitude of the binding energy of the pair (I-V). The variation of the impurity (or solute) correlation factor versus the annihilation frequency of the pair (I-V) was found to be similar to that obtained analytically.

Monte Carlo Calculation of Correlation Factors and Concentration Profiles for Interstitial-Substitutional Diffusion Mechanism with Impurity-Vacancy Interaction in the FCC Lattice. A.Hasnaoui, A.Menai: Physica Status Solidi B, 2002, 233[1], 158-69