Surface Nucleation in the Freezing of Gold Nanoparticles

TL;DR

This study uses molecular simulations to investigate the nucleation process during gold nanoparticle freezing, revealing that surface effects and line tension significantly influence the formation of solid embryos.

Contribution

It introduces a partial wetting model showing that embryo growth occurs at the vapor-surface interface, challenging classical nucleation assumptions.

Findings

Embryos grow at the vapor-surface interface for all temperatures studied.

Classical nucleation model fails to predict the free energy barrier shape.

Line tension is crucial in the freezing process of gold nanoparticles.

Abstract

We use molecular simulation to calculate the nucleation free energy barrier for the freezing of a 456 atom gold cluster over a range of temperatures. The results show that the embryo of the solid cluster grows at the vapor-surface interface for all temperatures studied and that the usual classical nucleation model, with the embryo growing in the core of the cluster, is unable to predict the shape of the free energy barrier. We use a simple partial wetting model that treats the crystal as a lens shaped nucleus at the liquid-vapor interface and find that the line tension plays an important role in the freezing of gold nanoparticles.