Structuring effects in binary nucleation: Molecular dynamics simulations and coarse-grained nucleation theory

Binary clusters formed by vapor-liquid nucleation are frequently nonhomogeneous objects in which components are not well mixed. The structure of a cluster plays an important role in nucleation and cluster growth. We demonstrate structuring effects by studying high-pressure nucleation and cluster growth in the n-nonane/methane mixture by means of molecular dynamics simulation. It is found that methane is squeezed out from the cluster core which is rich with n-nonane molecules. At typical simulation conditions-pressure 60 bar, temperature 240 K, nucleation rate J ? 1026 cm?3 s?1-the mole fraction of methane in the critical cluster reaches 80%, being much higher than its equilibrium bulk liquid fraction at the same pressure and temperature. These observations are supported by the recently formulated coarse-grained theory of binary nucleation