Phase diagram of supercooled water confined to hydrophilic nanopores

TL;DR

This paper develops a phase diagram for supercooled water confined in hydrophilic nanopores, revealing how pore size influences water's phase behavior, including liquid, crystalline, and glassy states, supported by experimental and simulation data.

Contribution

It provides a novel phase diagram for confined supercooled water, integrating experimental observations and simulations to understand phase stability in nanopores.

Findings

Large pores (>1 nm) show liquid and crystalline phases with abrupt transitions.

Small pores stabilize amorphous and glassy states at low temperatures.

Experimental results on supercooled water are explained by the phase diagram.

Abstract

We present a phase diagram for water confined to cylindrical silica nanopores in terms of pressure, temperature and pore radius. The confining cylindrical wall is hydrophilic and disordered, which has a destabilizing effect on ordered water structure. The phase diagram for this class of systems is derived from general arguments, with parameters taken from experimental observations and computer simulations and with assumptions tested by computer simulation. Phase space divides into three regions: a single liquid, a crystal-like solid, and glass. For large pores, radii exceeding 1 nm, water exhibits liquid and crystal-like behaviors, with abrupt crossovers between these regimes. For small pore radii, crystal-like behavior is unstable and water remains amorphous for all non-zero temperatures. At low enough temperatures, these states are glasses. Several experimental results for supercooled water can be understood in terms of the phase diagram we present.