Monte Carlo simulation of homogeneous binary vapor–liquid nucleation: Mutual enhancement of nucleation in a partially miscible system

Authors

S. Yoo, University of Nebraska-Lincoln
K.J. Oh, University of Nebraska-Lincoln
Xiao Cheng Zeng, University of Nebraska-LincolnFollow

Date of this Version

11-8-2001

Comments

Published by American Institute of Physics. J. Chem. Physics VOLUME 115, NUMBER 18, 8 NOVEMBER 2001. ©2001 American Institute of Physics. Permission to use. http://jcp.aip.org/.

Abstract

Gibbs free energy of ij-cluster formation ΔG_ij is obtained via the relation n_ij=Ne^{-ΔG_ij /k_BT}, where N is the number of molecules in the system, T is temperature, and kB is the Boltzmann constant. The saddle point on the free energy surface ΔG_ij versus i and j provides a measure of the activation barrier to nucleation ΔG *. A statistical mechanical formula of ΔG_ij is derived based on the physical-cluster theory of nucleation, and from which a molecular interpretation of ΔG_ij is given. We applied the Monte Carlo method to investigate the mutual enhancement of nucleation in a binary model system which is composed of spherical Lennard-Jones monomers and rigid Lennard-Jones dimers consisting of a monophilic atom and a monophobic atom. This model system bears some qualitative similarity to the partially miscible water/higher alcohol systems in which the mutual enhancement of nucleation has been observed experimentally. The simulation confirms the existence of mutual enhancement of nucleation in monomer-rich vapors, as originally predicted by Napari and Laaksonen from a density-functional theory [Napari and Laaksonen, Phys. Rev. Lett. 84, 2184 (2000)]. The nucleation enhancement is also seen in dimer-rich vapors at high supersaturations.