Density functional theory calculations were performed to study the interaction of carbon with He-vacancy complexes in α-Fe. Using the density functional theory predictions, a rate theory model that accounts for the evolution of carbon, helium, and defects created during irradiation was developed to explore the influence of carbon on the kinetics of He diffusion and clustering after implantation in α-Fe. This density functional theory-based rate theory model predicts that carbon not only influences vacancy (V) migration but also He desorption, enhancing He mobility in particular for low V/C ratios. The reason for this behavior was mainly the formation of VC and VC2 complexes, which significantly reduces the mobility of vacancies with respect to pure Fe, inhibiting the formation of higher order clusters, i.e., HenVm, and increasing thus the number of He at substitutional positions at room temperature. Assuming reasonable values of carbon concentration, existing desorption experimental results were successfully reproduced and interpreted, where all of the energetic parameters for the relevant reactions were obtained from first-principles calculations. In addition, the study provided a detailed explanation of the various He migration mechanisms that prevail under the experimental conditions considered.

Influence of Carbon on the Kinetics of He Migration and Clustering in α-Fe from First Principles. C.J.Ortiz, M.J.Caturla, C.C.Fu, F.Willaime: Physical Review B, 2009, 80[13], 134109