Determination of depths of multiple traps for interstitials and their influence on diffusion kinetics

Trapping of interstitial atoms by foreign substitutional atoms is a phenomenon that significantly influences the chemistry of the system as well as the diffusivity of the interstitial components. In their previous paper (Svoboda et al 2013 Modelling Simul. Mater. Sci. Eng. 21 065012), the present authors determined the trapping energy and the chemical diffusion coefficient of an interstitial component for a dilute system by assuming only one type of trap. This model is now generalized for non-dilute systems, and it accounts for the fact that each interstitial trap position can be influenced by several foreign atoms. The model is applied to a non-dilute Fe–Cr–rather dilute C system neglecting interstitial–interstitial interactions. Fitting of the chemical potential of the interstitial component given by the model to that given by thermodynamic databases provides parameters allowing calculation of the depth of the trap depending on the number of foreign atoms surrounding the trap position. The results of fitting indicate that the model is physically sound. Based on an established concept, subsequently, the chemical diffusion coefficient of the interstitial is calculated for different chemical compositions.