Liquid Polymorphism and Double Criticality in a Lattice Gas Model

TL;DR

This paper investigates a lattice gas model for associating liquids, revealing complex phase diagrams with liquid-liquid transitions and double critical points, influenced by competing interactions and their relative strengths.

Contribution

It introduces a two-dimensional lattice model combining ice-like and Van der Waals interactions, analyzing phase behavior through mean-field and simulation methods.

Findings

Presence of liquid-liquid critical points and phase transitions.

Disappearance of double criticality as interaction ratio decreases.

Potential relevance to molecular liquid behaviors.

Abstract

We analyze the possible phase diagrams of a simple model for an associating liquid proposed previously. Our two-dimensional lattice model combines oreintati onal ice-like interactions and \"{}Van der Waals\"{} interactions which may be repulsive, and in this case represent a penalty for distortion of hydrogen bonds in the presence of extra molecules. These interactions can be interpreted in terms of two competing distances, but not necessarily soft-core. We present mean -field calculations and an exhaustive simulation study for different parameters which represent relative strength of the bonding interaction to the energy penalty for its distortion. As this ratio decreases, a smooth disappearance of the doubl e criticality occurs. Possible connections to liquid-liquid transitions of molecul ar liquids are suggested.