Liquid polymorphism, order-disorder transitions and anomalous behavior: a Monte Carlo study of the Bell-Lavis model for water

TL;DR

This study uses Monte Carlo simulations to analyze the Bell-Lavis model for water, revealing a continuous liquid-liquid transition characterized as an order-disorder transition in the Ising universality class, and exploring anomalous density behavior.

Contribution

It demonstrates that the water-like transition in the Bell-Lavis model is continuous and identifies it as an order-disorder transition, challenging previous mean-field predictions.

Findings

The liquid-liquid transition is continuous, not first-order.

The transition belongs to the Ising universality class.

Density maxima in the HDL phase are stabilized by fluctuations.

Abstract

The Bell-Lavis model for liquid water is investigated through numerical simulations. The lattice-gas model on a triangular lattice presents orientational states and is known to present a highly bonded low density phase and a loosely bonded high density phase. We show that the model liquid-liquid transition is continuous, in contradiction with mean-field results on the Husimi cactus and from the cluster variational method. We define an order parameter which allows interpretation of the transition as an order-disorder transition of the bond-network. Our results indicate that the order-disorder transition is in the Ising universality class. Previous proposal of an Ehrenfest second order transition is discarded. A detailed investigation of anomalous properties has also been undertaken. The line of density maxima in the HDL phase is stabilized by fluctuations, absent in the mean-field solution.