TIME-DEPENDENT DENSITY-FUNCTIONAL THEORY AND THE KINETICS OF LATTICE-GAS SYSTEMS IN CONTACT WITH A WALL

We develop an improved mean-held theory which allows us to describe th e diffusive dynamics near phase transformations in condensed systems. Starting from a master equation for a stochastic lattice gas we obtain evolution equations on the single-particle level, whose stationary so lutions in principle are consistent with the exact equilibrium statist ics. Our method, which generalizes an approach proposed earlier, is ba sed on a combination of a local equilibrium assumption and the lattice version of classical density functional theory. In the continuum limi t, which is worked out for attractive interactions, generalized Cahn-H illiard-type equations are recovered. Microscopic kinetic coefficients can be identified, which in general depend on the instantaneous local correlations in the nonequilibrium state. Moreover we study semi-infi nite systems interacting with a planar wall and derive the appropriate boundary conditions to be imposed on the continuum equations. Applica tions to problems of the kinetics of phase changes influenced by a nea r wall are pointed out. (C) 1998 American Institute of Physics.