Monte Carlo simulations were made of the behavior of so-called non-equilibrium tracer and collective diffusion coefficients in a lattice-gas model, involving attractive nearest-neighbour interactions, as the system evolved from an initial random state to the (1 x 1) ordered state at temperatures, T/Tc < 1. The dependence of the mean-square displacement upon time, and collective diffusion from relaxation of the non-equilibrium structure factor, were calculated for sub-intervals of time; under the assumption that quasi-equilibrium conditions held. The time-dependent non-equilibrium diffusion coefficients were determined, and time-dependent activation energies were deduced.

Diffusion Studies in Non-Equilibrium Systems with Attractive Interactions. E.Arapaki, P.Argyrakis, M.C.Tringides: Physical Review B, 2000, 62[12], 8286-94