OBSERVATION OF DROPLET GROWTH AND COALESCENCE IN PHASE-SEPARATING LENNARD-JONES FLUIDS

Molecular dynamics computer simulations of the vapor/liquid phase tran sition of a Lennard-Jones fluid are presented. The simulations reveal that, in the late stage of the transition, clusters grow linearly with time. This linear growth regime can be described by an extension of t he Lifshitz-Slyozov theory with an asymptotic droplet growth power law t(1/3). This growth mode is interrupted by the coalescence of cluster s, whose motions have Brownian character. The Brownian nature of the c luster trajectories is a consequence of internal degrees of freedom ra ther than of environmental noise. The diffusion coefficients of these clusters, as a function of cluster size, are found to be well represen ted by the kinetic theory of the ideal gas.