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Multicomponent Diffusion Revisited: Pair-Mobilities and Consistent Definition of Diffusion Coefficients

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Document pages: 32 pages

Abstract: The recently proposed pair-exchange concept for multicomponent diffusion is analyzed in detail. The concept defines the differences of chemical potential gradients of two elements as general driving forces for interdiffusion and defines the corresponding proportionality coefficients as pair-mobilities for atomic exchange fluxes of a pair of elements at the mesoscopic scale. The total fluxes of alloying elements are given as the sum over corresponding pair-contributions, which rely on an interdependent set of forces to maintain a meaningful symmetric form. Onsager s reciprocal relations are satisfied as well as the consistency between description of chemical- and tracer-diffusion. It is confirmed that a consistent definition of interdiffusion coefficients requires the fulfillment of the Gibbs-Duhem relation by the applied thermodynamic Gibbs energy description.

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