Gas-Liquid Nucleation in Two Dimensional System

TL;DR

This study investigates 2D gas-liquid nucleation using Monte Carlo simulations, revealing that classical nucleation theory significantly underestimates the free energy barrier and overestimates line tension, highlighting dimensional differences in nucleation behavior.

Contribution

The paper provides detailed simulation data on 2D nucleation, demonstrating the failure of classical nucleation theory in 2D and emphasizing the importance of potential truncation.

Findings

Classical nucleation theory underestimates the free energy barrier by up to 70% in 2D.

Large potential cut-offs are necessary for accurate 2D nucleation results.

CNT overestimates line tension and is less reliable in 2D than in 3D.

Abstract

We study the nucleation of the liquid phase from a supersaturated vapor in two dimensions (2D). Using different Monte Carlo simulation methods, we calculate the free energy barrier for nucleation, the line tension and also investigate the size and shape of the critical nucleus. The study is carried out at an intermediate level of supersaturation(away from the spinodal limit). In 2D, a large cut-off in the truncation of the Lennard-Jones (LJ) potential is required to obtain converged results, whereas low cut-off (say, $2.5\sigma$ is generally sufficient in three dimensional studies, where $\sigma$ is the LJ diameter) leads to a substantial error in the values of line tension, nucleation barrier and characteristics of the critical cluster. It is found that in 2D, the classical nucleation theory (CNT) fails to provide a reliable estimate of the free energy barrier. It underestimates the barrier by as much as 70% at the saturation-ratio S=1.1 (defined as S=P/PC, where PC is the coexistence pressure at reduced temperature $T^{\star}= 0.427$). Interestingly, CNT has been found to overestimate the nucleation free energy barrier in three dimensional (3D)systems near the triple point. In fact, the agreement with CNT is worse in 2D than in 3D. Moreover, the existing theoretical estimate of the line tension overestimates the value significantly.