Communication: Two-structure thermodynamics unifying all scenarios for water anomalies

TL;DR

This paper presents a unified thermodynamic framework explaining water's anomalies through a two-structure equation of state that incorporates criticality and re-entrant spinodal behavior.

Contribution

It introduces a novel two-structure equation of state that unifies different scenarios explaining water's anomalies, emphasizing the role of criticality.

Findings

Water anomalies are linked to criticality rather than re-entering spinodal.

The new model unifies vapor-liquid spinodal and re-entrant scenarios.

Response functions diverge due to criticality in the proposed framework.

Abstract

Anomalous behavior of water in superooled region (namely decrease of density and sharp increase of response functions at atmospheric pressure) are manly associated with either existence of liquid-liquid criticality or re-entering vapor-liquid spinodal into positive pressure. Despite different origin both scenarios introduce divergence of the response functions. We articulate in the communication that the criticality is behind water anomalies, water has normal vapor-liquid spinodal and that the re-entering feature was predicted because of curved density surface as a consequence of existence of critical point. We can proof this by new two structure equation of state with criticality resulting from non-ideal mixing of two states and a background state being modeled by exactly the same equation of state which was deployed for predicting of vapor-liquid spinodal while formulating the re-entering scenario.