Monte Carlo simulation study of droplet nucleation

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Computational Physics

Background:

• Nucleation is a critical phenomenon in phase transitions.
• Classical nucleation theory (CNT) provides a framework but has limitations.
• Understanding nucleation barriers is essential for predicting phase transition rates.

Purpose of the Study:

• To rigorously study nucleation barriers for droplets in Lennard-Jones fluid using advanced simulation techniques.
• To assess the accuracy of classical nucleation theory and the Tolman equation for small clusters.
• To provide quantitative data on droplet surface tension and its dependence on size.

Main Methods:

• Rigorous Monte Carlo simulations employing the gauge cell method.
• Ghost field method for precise computation of cluster free energy and nucleation barriers.
• Analysis of critical clusters in the size range of two to six molecular diameters.

Main Results:

• The capillarity approximation, corrected for vapor nonideality and liquid compressibility, reasonably estimates critical cluster size.
• This approximation is insufficient for accurate prediction of nucleation barriers and nucleation rates.
• The Tolman equation fails to describe the size-dependent droplet surface tension for droplets smaller than four molecular diameters.
• Integration of the Irving-Kirkwood pressure tensor underestimates nucleation barriers for small clusters.

Conclusions:

• Advanced Monte Carlo simulations offer high precision for nucleation barrier studies.
• Classical nucleation theory and its corrections have limited applicability for quantitative nucleation rate predictions.
• The size dependence of surface tension in small droplets deviates significantly from Tolman's equation.