Polymorphism, thermodynamic anomalies and network formation in an atomistic model with two internal states

TL;DR

This study uses molecular dynamics to explore a 2D particle model with internal states, revealing complex phase behavior including polymorphism and anomalies similar to water and silica.

Contribution

It introduces a simple two-internal-state particle model that captures key features of network-forming liquids, expanding understanding of their thermodynamic behavior.

Findings

Rich phase diagram with polymorphism

Presence of thermodynamic anomalies

Model mimics properties of water and silica

Abstract

Using molecular dynamics simulations we study the temperature-density phase diagram of a simple model system of particles in two dimensions. In addition to translational degrees of freedom, each particle has two internal states and interacts with a modified Lennard-Jones potential which depends on relative positions as well as the internal states. We find that, despite its simplicity, the model has a rich phase diagram showing many features of common network-forming liquids such as water and silica, including polymorphism and thermodynamic anomalies. We believe our model may be useful for studies concerning generic features of such complex liquids.