Molecular-dynamics study of the density scaling of inert gas condensation

The initial stages of vapor condensation of Ge in the presence of a cold Ar atmosphere were studied by molecular-dynamics simulations. The state variables of interest included the densities of condensing vapor and gas, the density of clusters, and the average cluster size, while the temperatures of the vapor and the clusters were separately monitored with time. Three condensation processes were explicitly identified: nucleation, monomeric growth, and cluster aggregation. Our principal finding is that both the average cluster size and the number of clusters scale with the linear dimension of the computation cell, L, and L-n, with the scaling parameter n approximate to 4, corresponding to a reaction order of nu approximate to 2.33. This small value of n is explained by an unexpected nucleation path involving the formation of Ge dimers via two-body collisions. (c) 2005 American Institute of Physics