A liquid-solid critical point in a simple monatomic system

TL;DR

This paper presents molecular dynamics evidence of a liquid-solid critical point in a simple monatomic system, challenging traditional views and showing continuous phase transformation involving mesoscopic order.

Contribution

It demonstrates the existence of a liquid-solid critical point in a simple monatomic system, revealing a continuous transition with mesoscopic order, contrary to traditional symmetry-based expectations.

Findings

Liquid-solid spinodal terminates at a critical point.

Isotropic liquid transforms into a mesophase with smectic-like order.

Structural proximity explains the critical behavior.

Abstract

It is commonly believed that the transition line separating a liquid and a solid cannot be interrupted by a critical point. This opinion is based on the traditional symmetry argument that an isotropic liquid cannot be continuously transformed into a crystal with a discrete rotational and translational symmetry. We present here a molecular-dynamics simulation of a simple monatomic system that demonstrates a liquid-solid spinodal terminating at a critical point. We show that, in the critical region, the isotropic liquid continuously transforms into a phase with a mesoscopic order similar to that of the smectic liquid crystals. We argue that the existence of both the spinodal and the critical point can be explained by the close structural proximity between the mesophase and the crystal. This indicates a possibility of finding a similar thermodynamic behaviour in gelating colloids, liquid crystals and polymers.