Free energy of formation of small ice nuclei near the Widom line in simulations of supercooled water

TL;DR

This study uses Monte Carlo simulations to analyze the free energy of small ice nuclei formation near the Widom line in supercooled water, revealing how thermodynamic anomalies influence ice nucleation.

Contribution

It provides the first detailed free energy profile of ice nuclei formation near the Widom line in supercooled water using ST2 potential simulations.

Findings

High free energy cost for ice nuclei formation near Widom line

Thermodynamic anomalies occur in a metastable liquid phase

Changes in free energy influence ice nucleation process

Abstract

The ST2 interaction potential has been used in a large number of simulation studies to explore the possibility of a liquid-liquid phase transition (LLPT) in supercooled water. Using umbrella sampling Monte Carlo simulations of ST2 water, we evaluate the free energy of formation of small ice nuclei in the supercooled liquid in the vicinity of the Widom line, the region above the critical temperature of the LLPT where a number of thermodynamic anomalies occur. Our results show that in this region there is a substantial free energy cost for the formation of small ice nuclei, demonstrating that the thermodynamic anomalies associated with the Widom line in ST2 water occur in a well-defined metastable liquid phase. On passing through the Widom line, we identify changes in the free energy to form small ice nuclei that illustrate how the thermodynamic anomalies associated with the LLPT may influence the ice nucleation process.