Molecular dynamics simulations of crystallization of hard spheres

TL;DR

This study uses molecular dynamics simulations to explore how gravitational forces, polydispersity, and bounding walls influence the crystallization process of hard spheres, providing insights relevant to colloidal and space-based experiments.

Contribution

It introduces a detailed simulation approach combining structure factor analysis and local invariants to study crystallization, benchmarking results against experiments and examining wall and gravity effects.

Findings

Bounding walls induce wall-nucleation and accelerate crystallization.

Gravity significantly affects crystallization dynamics.

Simulation results align with experimental nucleation rates.

Abstract

We have carried out molecular dynamics simulations of the crystallization of hard spheres modelling colloidal systems that are studied in conventional and space-based experiments. We use microscopic probes to investigate the effects of gravitational forces, polydispersity and of bounding walls on the phase structure. The simulations employed an extensive exclusive particle grid method and the type and degree of crystalline order was studied in two independent ways: by the structure factor, as in experiments, and through local rotational invariants. We present quantitative comparisons of the nucleation rates of monodisperse and polydisperse hard sphere systems and benchmark them against experimental results. We show how the presence of bounding walls leads to wall-induced nucleation and rapid crystallization and discuss the role of gravity on the dynamics of crystallization.