Heterogeneous condensation of the Lennard-Jones vapor onto a nanoscale seed particle

TL;DR

This study uses molecular dynamics simulations to analyze how nanoscale seed particles influence the heterogeneous condensation of Lennard-Jones vapor, revealing effects on nucleation rates and free energy barriers.

Contribution

It introduces a detailed simulation analysis of heterogeneous nucleation on nanoscale seeds and develops a phenomenological model to describe the process.

Findings

Weakly interacting seeds minimally affect small cluster formation.

Seeds lower the free energy barrier for larger clusters, increasing nucleation rate.

Classical nucleation theory overestimates the barrier size in heterogeneous conditions.

Abstract

The heterogeneous condensation of a Lennard-Jones vapor onto a nanoscale seed particle is studied using molecular dynamics simulations. Measuring the nucleation rate and the height of the free energy barrier using the mean first passage time method shows that the presence of a weakly interacting seed has little effect on the work of forming very small cluster embryos but accelerates the rate by lowering the barrier for larger clusters. We suggest that this results from a competition between the energetic and entropic features of cluster formation in the bulk and at the heterogeneity. As the interaction is increased, the free energy of formation is reduced for all cluster sizes. We also develop a simple phenomenological model of film formation on a small seed that captures the general features of the nucleation process for small heterogeneities. A comparison of our simulation results with the model shows that heterogeneous classical nucleation theory provides a good estimate of the critical size of the film but significantly over-estimates the size of the barrier.