Homogeneous and heterogeneous nucleation of water vapor: A comparison using molecular dynamics simulation

Abstract

Using simple point charge/extended potential for water–water and a potential model for ion–water interaction, homogeneous and heterogeneous nucleation of water vapor are investigated with molecular dynamics simulation at 350K under supersaturation ratio of 8.9341 and 6.5000. The simulation results show the size and sign preference for ions, which is the rate of nucleation is higher for smaller negative ions. In spite of previous works which the position of ion was fixed in the center of a spherical cluster and the nucleation rate was derived from cluster formation free energy, we consider the ion as the second component which can move with no limitation on its position and the nucleation rate is calculated directly from the simulation data. The effect of supersaturation of water vapor on nucleation rate in presence of positive ions is also studied which indicates the important role of the ion presence in the nucleation process at low supersaturations.