Exact macroscopic description of phase segregation in model alloys with long range interactions

We derive an exact nonlinear nonlocal macroscopic equation for the time evolution of the conserved order parameter ρ(r, t) of a microscopic model binary alloy undergoing phase segregation: a d-dimensional lattice gas evolving via Kawasaki exchange dynamics, satisfying detailed balance for a Hamiltonian with a long range pair potential [Formula presented]. The macroscopic evolution is on the spatial scale γ-1 and time scale γ-2, in the limit γ→0. The domain coarsening, described by interface motion, is similar to that obtained from the Cahn-Hilliard equation. © 1996 The American Physical Society.