Revisiting waterlike network-forming lattice models

TL;DR

This paper revisits lattice models of waterlike network-forming fluids, using semi-analytical methods to analyze phase diagrams and clarify the origin of thermodynamic anomalies, revealing artifacts caused by homogeneity assumptions.

Contribution

The study extends previous semi-analytical calculations to various models, identifying common ordered phases and addressing artifacts in waterlike anomaly predictions.

Findings

Ordered phases are consistent across models.

Waterlike anomalies are artifacts of homogeneity assumptions.

A method to overcome analytical limitations is proposed.

Abstract

In a previous paper [J. Chem. Phys. 129, 024506 (2008)] we studied a 3 dimensional lattice model of a network-forming fluid, recently proposed in order to investigate water anomalies. Our semi-analytical calculation, based on a cluster-variation technique, turned out to reproduce almost quantitatively several Monte Carlo results and allowed us to clarify the structure of the phase diagram, including different kinds of orientationally ordered phases. Here, we extend the calculation to different parameter values and to other similar models, known in the literature. We observe that analogous ordered phases occur in all these models. Moreover, we show that certain "waterlike" thermodynamic anomalies, claimed by previous studies, are indeed artifacts of a homogeneity assumption made in the analytical treatment. We argue that such a difficulty is common to a whole class of lattice models for water, and suggest a possible way to overcome the problem.