Homogeneous nucleation and growth from highly supersaturated vapor by molecular dynamics simulation

摘要

The formation of particles and aerosols is an important step in several industrial as well as environmental processes. Its formation can be an undesired phenomenon, for example, in thermal separation processes, in turbines or the discharge of environmentally problematic aerosols from industrial processes. However, it can also be the central process in case of the production of nanoparticles or disperse systems such as pharmaceutical nanodispersions. The atmosphere and hence the climate is influenced by the presence of several different aerosols. While primary aerosols are particles that are emitted into the atmosphere, secondary aerosols are formed in the atmosphere by nucleation and growth. One possible way of particle and aerosol formation is homogeneous nucleation caused by density fluctuations in supersaturated systems. This is the first step followed by surface growth and initial coalescence processes. The initial steps happen on the nanometer scale and can be investigated by molecular simulation, which enable the modeling and analysis based on molecular interactions. Here, different molecular dynamics methods for the investigation of nucleation and particle growth are discussed. The focus is on various substances such as argon, alkanols, and metals. The simulations start at highly supersaturated states in the metastable region of the phase diagram.