Correlation between 2D Square Ice and 3D Bulk Ice by Critical Crystallization Pressure

TL;DR

This study uses molecular dynamics simulations to explore how the critical crystallization pressure of 2D square ice varies with nanocapillary size, revealing a direct correlation with 3D bulk ice and identifying an unfreezable threshold.

Contribution

It uncovers the size-dependent variation of critical crystallization pressure in 2D square ice and establishes a direct link to 3D bulk ice behavior using all-atom simulations.

Findings

Critical crystallization pressure depends strongly on nanocapillary size.

As capillary size increases, pressure converges to bulk ice values.

An unfreezable threshold explains the limit of nanocapillary width for ice formation.

Abstract

Low-dimensional ice trapped in nanocapillaries is a fascinating phenomenon and is ubiquitous in our daily lives. As a decisive factor of the confinement effect, the size of nanocapillary significantly affects the critical crystallization pressure and crystalline structure, especially for multi-layered ices. By choosing square ice as a typical two-dimensional (2D) multi-layered ice pattern and using all-atom molecular dynamics simulations, we further unveil the variation mechanism of critical crystallization pressure with the nanocapillary size. The results show a strong dependence of the critical crystallization pressure on the size of the graphene sheet for monolayer, bilayer, and trilayer square ice. The quasi-macroscopic crystallization pressure, the actual pressure of water molecules, and the freezable region between them are all strongly dependent on the nanocapillary width. As the size of the capillary becomes larger in all three directions, the critical crystallization pressure converges to the true macroscopic crystallization pressure, which is very close to the value of the crystallization pressure for bulk ice. A direct correlation is established between 2D square ice and three-dimensional (3D) bulk ice by the critical crystallization pressure. There is an unfreezable threshold for crystallizing spontaneously in practice when the quasi-macroscopic crystallization pressure is equal to the actual pressure, which can explain the limit of nanocapillary width for multi-layered ice.