Kinetic ising model study of phase separation in binary alloys

The decomposition of binary alloys after a sudden quench below the critical temperature of unmixing is studied on a microscopic basis, using a stochastic model analog to the Kawasaki spin exchange Ising model. For interactions of long range the model reduces to the standard phenomenological equation. We relate this nonlinear equation to our recent treatment of the time-dependent Ginzburg-Landau theory, and calculate the nonequilibrium relaxation functions. For interactions of short range we present some computer simulations. As example, we treat a 55×55 square lattice, with a gradient in the chemical potential. Details are given for the relaxation process, which is a coarsening at the initial stage of the decomposition, while later the gradient produces a more macroscopic phase separation.