Structural properties and liquid spinodal of water confined in a hydrophobic environment

TL;DR

This study uses computer simulations to explore the thermodynamic properties of water confined in a hydrophobic environment, revealing preserved hydrogen bonding and shifts in critical lines compared to bulk water.

Contribution

It provides new insights into the behavior of supercooled water under hydrophobic confinement, including the calculation of the liquid spinodal and density maximum lines.

Findings

Hydrogen bond network remains largely intact under confinement.

The spinodal line decreases monotonically with temperature.

Confinement shifts the density maximum and spinodal to higher pressures and lower temperatures.

Abstract

We present the results of a computer simulation study of thermodynamical properties of TIP4P water confined in a hydrophobic disordered matrix of soft spheres upon supercooling. The hydrogen bond network of water appears preserved in this hydrophobic confinement. Nonetheless a reduction in the average number of hydrogen bonds due to the geometrical constraints is observed. The liquid branch of the spinodal line is calculated from 350 K down to 210 K. The same thermodynamic scenario of the bulk is found: the spinodal curve is monotonically decreasing. The line of maximum density bends avoiding a crossing of the spinodal. There is however a shift both of the line of maximum density and of the spinodal toward higher pressures and lower temperatures with respect to bulk.