Nonclassical Nucleation Pathways in Liquid Condensation Revealed by Simulation and Theory

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Nucleation is fundamental to phase transitions, including liquid condensation.
• Classical nucleation theory often assumes critical clusters have bulk liquid density, a simplification potentially limiting accuracy.

Purpose of the Study:

• To precisely characterize droplet nucleation from supersaturated gas using advanced simulations.
• To investigate the density of critical clusters during nucleation.
• To develop and validate a refined nucleation theory.

Main Methods:

• State-of-the-art rare-event sampling simulations were employed.
• Atomistic simulations were used to observe nucleation pathways.
• A two-variable nucleation theory, accounting for cluster density, was developed and tested.

Main Results:

• Critical clusters were found to have a density significantly different from bulk liquid.
• A nonclassical nucleation pathway involving simultaneous growth and densification was observed.
• The two-variable nucleation theory quantitatively reproduced simulation results for nucleation rates and critical properties.

Conclusions:

• Cluster density is a critical variable in nucleation phenomena.
• The developed two-variable theory offers a more accurate description of nucleation pathways and rates.
• This work refines nucleation theory by moving beyond single-variable approximations.