Water-like anomalies as a function of tetrahedrality

TL;DR

This study explores how varying tetrahedral interactions influence water-like anomalies, revealing a new phase transition and linking phase diagram shape to thermodynamic and dynamic properties through local structural order.

Contribution

It systematically analyzes the Stillinger-Weber potential's behavior as a function of tetrahedral interaction strength, uncovering a new re-entrant spinodal line and providing a two-state model explanation.

Findings

Discovery of a re-entrant spinodal line at low tetrahedral interaction strength.

Transition from Non-Arrhenius to Arrhenius dynamical behavior.

Correlation between phase diagram shape and local structural ordering.

Abstract

Tetrahedral interactions describe the behaviour of the most abundant and technologically important materials on Earth, such as water, silicon, carbon, germanium, and countless others. Despite their differences, these materials share unique common physical behaviours, such as liquid anomalies, open crystalline structures, and extremely poor glass-forming ability at ambient pressure. To reveal the physical origin of these anomalies and their link to the shape of the phase diagram, we systematically study the properties of the Stillinger-Weber potential as a function of the strength of the tetrahedral interaction $\lambda$. We uncover a new transition to a re-entrant spinodal line at low values of $\lambda$, accompanied with a change in the dynamical behaviour, from Non-Arrhenius to Arrhenius. We then show that a two-state model can provide a comprehensive understanding on how the thermodynamic and dynamic anomalies of this important class of materials depend on the strength of the tetrahedral interaction. Our work establishes a deep link between the shape of phase diagram and the thermodynamic and dynamic properties through local structural ordering in liquids, and hints at why water is so special among all substances.