# A doubly associated reference perturbation theory for water

## TL;DR

This paper introduces a new classical perturbation theory for water that accounts for tetrahedral symmetry transition and accurately predicts water's thermodynamic anomalies, including density maximum and compressibility minima.

## Contribution

The paper develops a self-consistent perturbation theory that incorporates structural transitions in water, going beyond traditional perturbation approaches.

## Key findings

- Accurately models water's thermodynamics
- Reproduces density maximum and minima in response functions
- Demonstrates improved understanding of water's anomalies

## Abstract

In this work we develop a new classical perturbation theory for water which incorporates the transition to tetrahedral symmetry in both the dispersion and hydrogen bonding contributions to the free energy. This transition is calculated self-consistently using Wertheim's thermodynamic perturbation theory. However, since the reference fluid structure to the hydrogen bonding theory itself depends on hydrogen bonding, the theory represents an approach which goes beyond perturbation theory. The theory is shown to accurately represent the thermodynamics of pure water. It is demonstrated that the new theory can reproduce the anomalous density maximum as well as minima in the isothermal compressibility and isobaric heat capacity.

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Source: https://tomesphere.com/paper/1903.09446