Tetrahedrality, hydrogen bonding and the density anomaly of the central force water model. A Monte Carlo study

TL;DR

This study uses Monte Carlo simulations to analyze the structural and thermodynamic properties of the CF1 water model, focusing on hydrogen bonding and tetrahedral order to explain water's density anomaly.

Contribution

It provides a detailed Monte Carlo analysis of the CF1 water model, highlighting the importance of hydrogen bonding and tetrahedral order in reproducing water's anomalies.

Findings

The model reproduces the intramolecular structure of water.

Hydrogen bonds are more accurately identified by an energetic criterion.

The model captures the density anomaly and vapor-liquid coexistence.

Abstract

Monte Carlo computer simulations in the canonical and grand canonical statistical ensemble were used to explore the properties of the central force (CF1) water model. The intramolecular structure of the H$_2$O molecule is well reproduced by the model. Emphasis was made on hydrogen bonding, and on the tehrahedral, $q$, and translational, $\tau$, order parameters. An energetic definition of the hydrogen bond gives more consistent results for the average number of hydrogen bonds compared to the one-parameter distance criterion. At 300 K, an average value of 3.8 was obtained. The $q$ and $\tau$ metrics were used to elucidate the water-like anomalous behaviour of the CF1 model. The structural anomalies lead to the density anomaly, with a good agreement of the model's density with the experimental $\rho(T)$ trends. The chemical potential-density projection of the model's equation of state was explored. Vapour-liquid coexistence was observed at sufficiently low temperatures.