Monte Carlo calculation of correlation factors and concentration profiles for interstitial-substitutional diffusion mechanism with impurity-vacancy interaction in the fcc lattice

Many diffusion systems present an anomalous fast diffusion (e.g. noble metals in lead; Zn, Pt, and Au in Si; Be in GaAs), which can be interpreted by mean's of the interstitial-substitutional exchange. In this work, the dissociative variant of this model, where the exchange between interstitial and substitutional configurations takes place with the interplay of vacancies, is simulated using the Monte Carlo method, that allows to avoid drastic simplifications used to solve analytically the set of reaction-diffusion equations describing this model. The interstitial-vacancy pair (I-V), where the binding energy is considered up to the second nearest neighbours, is considered. The results show, that the penetration profiles change their shape from two- to three-stages profiles depending on the magnitude of the binding energy of the pair (I-V). The variation of the impurity (or solute) correlation factor f versus the annihilation frequency of the pair (I-V) is found to be similar to that obtained analytically. The time evolution of the penetration profiles is also investigated.