Surface segregation of interacting atoms: analytical approach using a thermodynamic model

Binary atomic interactions are included in the thermodynamic Bragg–Williams model to study the cosegregation of different species of atoms in a multi-component alloy. The kinetics of segregating atoms is described by a set of mutually connected diffusion equations with boundary condition determined by instantaneously equalizing chemical potentials. This model allows analytical solution if t→0 and t→∞. For specific values of parameters our solution shows the approach to equilibrium through a quasi-equilibrium state, that is, the phenomenon of delayed segregation which has been recently analyzed by Jäger in the framework of the quasi-chemical approximation. We also predict a phenomenon of the nonmonotonic segregation.