Molecular dynamics simulation of heterogeneous nucleation at a structureless solid surface

The nucleation at a planar surface with attraction is investigated by molecular dynamics and compared with the corresponding homogeneous nucleation [J. Chem. Phys. 115, 8913 (2001)]. The attraction caused an increased vapor density near the surface which favors nucleation even for a weak attraction. The contact angle (Young's angle) for the critical nucleus cannot be obtained from Young's equation by using the equilibrium values for the tensions, due to the overlap of the solid-liquid interface with the liquid gas interface near the line of contact. After onset of nucleation the droplets grow algebraically with an increase of particles with a time exponent approximate to1.25, and different from the Lifshitz-Slyozov growth. For strong attractions the system undergoes a first-order prewetting transition to a thin two-dimensional-like layer of a thickness of only a few particle diameters. This happens at densities less than the density of saturated bulk vapor. The dynamics of prewetting behaves qualitatively as the homogeneous and heterogeneous nucleation and with the onset of prewetting by crossing an activation free energy barrier. (C) 2002 American Institute of Physics.