Pore emptying transition during nucleation in hydrophobic nanopores

TL;DR

This study uses the 2D Ising model to investigate nucleation pathways in hydrophobic nanopores, revealing a pore emptying transition and how pore width influences nucleation sites and mechanisms.

Contribution

It uncovers the pore emptying transition phenomenon and details how pore size affects nucleation pathways in hydrophobic nanopores.

Findings

Nucleation occurs outside narrow pores.

Nucleation begins inside wide pores.

Pore emptying transition observed at intermediate widths.

Abstract

Using the 2D Ising model we study the generic properties of nucleation in hydrophobic nanopores. To explore the pathways to nucleation of a spin-up phase from a metastable spin-down phase we perform umbrella sampling and transition path sampling simulations. We find that for narrow pores the nucleation occurs on the surface outside the pore. For wide pores the nucleation starts in the pore, and continues outside the filled pore. Intriguingly, we observe a pore emptying transition for a range of intermediate pore widths: a pre-critical nucleus fills the pore, continues to expand outside of the filled pore, but then suddenly gets expelled from the pore before reaching its critical size.