Monte-Carlo simulations of spinodal ordering and decomposition in compositionally modulated alloys

The early-stage kinetics of interdiffusion in compositionally modulated films have been studied by Monte-Carlo simulations on an Ising lattice in two and three dimensions, using nearest-neighbor interactions. For a negative heat of mixing and below the order-disorder transition temperature, if a short-wavelength modulation is along a direction that is not consistent with long-range order, then its temporal evolution does not follow the Cahn-Hilliard-Cook theory. The modulation amplitude decreases as a function of time, rather than increases; i.e., no one-dimensional spinodal ordering is observed. This disagreement with the theory implies that ordering in three dimensions cannot be described by a one-dimensional theory.