Numerical Simulation of Stationary Nucleation in a Wide Range of Supersaturations Taking into Account Thermal Effects

Abstract

The molecular dynamics method is employed to solve the problem of stationary vapor–liquid nucleation at a constant number of particles interacting via the Lennard-Jones potential for the cases of both isothermal and nonisothermal nucleation in a wide range of vapor supersaturations. A special simulation approach is used, in which clusters that have reached a certain size are removed from the system, while particles composing them are returned as monomers. The temperature distribution over cluster sizes is determined. It is found that the temperature somewhat decreases beginning from its value corresponding to monomers; however, as the cluster size approaches a critical value, it returns to its initial level and, then, rapidly increases. The temperature distribution over cluster sizes governs the distribution of their number densities and controls vapor nonideality, thus significantly affecting the nucleation rate. It is shown that the knowledge of the cluster temperature is of critical importance for analytical models, as it enables one to accurately determine the vapor supersaturation and the actual nonisothermal nucleation rate. The nucleation rates and critical cluster sizes determined for the isothermal and nonisothermal cases have shown satisfactory agreement with a theoretical model predicting a decrease in the nucleation rate under the nonisothermal conditions.