Molecular dynamics simulation of nucleation in the binary mixture n-nonane/methane.

Vapor-liquid nucleation in the binary system n-nonane/methane is investigated by molecular dynamics simulation. The supersaturation is achieved by cooling down the system during the expansion in order to closely mimic the real process. Binary clusters formed by nucleation are frequently inhomogeneous objects in which components are not well mixed. By studying high-pressure nucleation and cluster growth in the n-nonane/methane mixture, we demonstrate the role of structuring effects in these processes. At typical simulation conditions-pressure 60 bar, temperature 240 K, and nucleation rate ∼10(26) cm(-3)s(-1)-the mole fraction of methane in the critical cluster reaches 80 percent, which is much higher than its equilibrium value in the bulk liquid at the same pressure and temperature. These observations are supported by the recently formulated coarse-grained theory for binary nucleation as well as by the experimental observations.