A diffuse interface model for the interfacial transfer coefficient

Based on an extension to non-equilibrium problems, of Cahn’s interface layer thermodynamics, we demonstrate that the matrix of transfer coefficients across a coherent interface between two phases, α and β, can be viewed as a correction to the Onsager’s matrix of mobility coefficients along the continuous concentration profile. The latter coefficients are defined along the equilibrium concentration profile in the interfacial layer and in the α- and β-phases. Combining the above definition with that of solute interfacial excess, we can define transfer coefficients relative to two components chosen arbitrarily, the values of which are intrinsic properties of the interfacial layer, independent of its precise location and thickness.