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 Ln, with the scaling parameter n≈4, corresponding to a reaction order of ν≈2.33. This small value of n is explained by an unexpected nucleation path involving the formation of Ge dimers via two-body collisions.
Bibliographical noteFunding Information:
The research was supported by the U.S. Department of Energy U.S. DOE Basic Energy Sciences, under Grant No. DEFG02-91ER45439 and the U.S. DOE through the University of California under Subgrant B341494, No. 73722, grants of computer time from the National Center for Supercomputing Applications and the National Energy Research Scientific Computing.