Abstract
Using the system consist of water and small number of sulfuric acid molecules, we performed molecular dynamics simulation of vapor-liquid nucleation and examined the impact of addition of sulfuric acid molecules on the homogeneous nucleation of the water vapor. The nucleation rate, the critical cluster size, the cluster formation free energy and the cluster structure were compared with that in the homogeneous case. It was found that sulfuric acid reduced the critical cluster size, but did not affect the barrier height of the nucleation. Correspondingly, the nucleation rate was observed to be only moderately accelerated. Also, the curve of the cluster formation free energy is rather different from homogeneous one, and indicates that the cluster larger than the critical size cannot grow rapidly. It was found that these observations come from the process of cluster growth. In the early phase, each sulfuric acid molecule rapidly forms a stable small cluster. This cluster is difficult to absorb monomer, and the main way of growth is the fusion of clusters. Because the fusion does not happen very often, cluster growth becomes slow.
