Kinetic Crystallisation Instability in Liquids with Short-Ranged Attractions

TL;DR

This study explores how liquids with very short-range attractions become kinetically unstable and crystallize rapidly, with molecular dynamics simulations showing that such liquids tend to crystallize within their structural relaxation times, especially away from critical points.

Contribution

The paper demonstrates that liquids with extremely short-range attractions are kinetically unstable and tend to crystallize quickly, challenging the notion of metastability in these systems.

Findings

Liquids with 6% attraction range crystallize within relaxation times.

Near criticality, density fluctuations affect stability.

Structural changes occur on relaxation timescales even close to critical points.

Abstract

Liquids in systems with spherically symmetric interactions are not thermodynamically stable when the range of the attraction is reduced sufficiently. However, these metastable liquids have lifetimes long enough that they are readily observable prior to crystallisation. Here we investigate the fate of liquids when the interaction range is reduced dramatically. Under these conditions, we propose that the liquid becomes kinetically unstable, i.e. its properties are non-stationary on the timescale of structural relaxation. Using molecular dynamics simulations, we find that in the square well model with range 6% of the diameter, the liquid crystallises within the timescale of structural relaxation for state points except those so close to criticality that the lengthscale of density fluctuations couples to the length of the simulation box size for typical system sizes. Even very close to criticality, the liquid exhibits significant structural change on the timescale of relaxation.