A novel anomalous region of water

TL;DR

This paper identifies a new region of anomalous behavior in water's properties, distinct from known critical points, supported by experimental data and molecular dynamics simulations showing current models' failure to capture this anomaly.

Contribution

The study discovers a previously unknown anomalous region in water's properties far from critical points, challenging existing models and understanding of water's behavior.

Findings

Discovery of a new anomalous region in water's properties

Experimental data shows maxima and minima far from critical points

Standard water models fail to reproduce this anomaly

Abstract

Water is the most important liquid in the Universe. At the same time it is the most anomalous liquid. It demonstrates several dozens of anomalies, among which are density anomaly, diffusion anomaly etc. Anomalous behavior of water is a topic numerous publications. However, most of the publications investigate the anomalous behavior of water in the vicinity of critical points: the liquid-gas critical point and the second hypothetical critical point in supercooled region. Here we analyze experimental data on such properties of water as heat capacity, speed of sound, dynamic viscosity and thermal conductivity. We show that these properties demonstrate anomalous maxima and minima in a region which is far from both critical points. Therefore, we find a novel region of anomalous properties of water (anomalous triangle) which cannot be related to critical fluctuations. We also perform a molecular dynamics simulations of this region with two common water models - SPC/E and TIP4P - and show that these models fail to describe the novel anomalous region.