Time scales of supercooled water and implications for reversible polyamorphism

TL;DR

This paper explores the complex dynamics and time scales of supercooled water, arguing that these imply limited correlation lengths and interfacial energies, thus challenging the existence of macroscopic liquid-liquid phase coexistence.

Contribution

It provides a time-scale based argument against liquid-liquid criticality and macroscopic phase coexistence in supercooled water.

Findings

Correlation lengths are bounded by a few nanometers.

Interfacial free energy cannot grow with macroscopic surface area.

Density fluctuations are limited to nano-scale transient domains.

Abstract

Deeply supercooled water exhibits complex dynamics with large density fluctuations, ice coarsening and characteristic time scales extending from picoseconds to milliseconds. Here, we discuss implications of these time scales as they pertain to two-phase coexistence and to molecular simulations of supercooled water. Specifically, we argue that it is possible to discount liquid-liquid criticality because the time scales imply that correlation lengths for such behavior would be bounded by no more than a few nanometers. Similarly, it is possible to discount two-liquid coexistence because the time scales imply a bounded interfacial free energy that cannot grow in proportion to a macroscopic surface area. From time scales alone, therefore, we see that coexisting domains of differing density in supercooled water can be no more than nano-scale transient fluctuations.