Molecular Dynamics Simulation of Heterogeneous Nucleation of a Liquid Droplet on a Solid Surface

Heterogeneous nucleation of a liquid droplet on a solid surface was simulated with the molecular dynamics method. Argon vapor was represented by 5,760 Lennard-Jones molecules and the solid surface was represented by one layer of 4,464 harmonic molecules with the constant temperature heat bath model using the phantom molecules. The potential parameter between a solid molecule and a vapor molecule was varied to reproduce several surface wettabilities. When the vapor-solid system was in equilibrium at 160 K, temperature of the solid surface was suddenly decreased to 100 K or 80 K by the phantom method. Observed nucleation rate, critical nucleus size and free energy needed for cluster formation were not much different from the prediction of the classical heterogeneous nucleation theory in case of smaller cooling rate. The discrepancy became considerable with the increase in cooling rate and with increase in surface wettability because of the spatial temperature distribution.