Atomic mobilities, diffusivities and simulation of diffusion growth in the Co–Si system

Atomic mobilities of both Co and Si in all the solid phases of the Co–Si system were obtained through assessments of experimentally determined diffusion coefficients from the present work and the literature by the DICTRA (diffusion-controlled transformations) simulation package. The first-principles calculations were performed to clarify the contradictory impurity diffusion coefficients of Co in Si by determining the diffusion activation energy. The concept of “average thermodynamic factor” was extended to model binary compounds with certain homogeneity ranges. Based on the atomic mobilities obtained, the diffusion growths of the compounds in wide temperature ranges were predicted. Comprehensive comparisons show that most of the experimental data resulting from diffusion phenomena are well reproduced by the parameters obtained. The approach is of general validity and applicable to establish mobility databases of technically important alloys.