Crystal Nucleation in binary hard-sphere mixtures: The effect of order parameter on the cluster composition

Ran Ni (1) , Frank Smallenburg (1) , Laura Filion (1) , Marjolein Dijkstra (2)

1 Universiteit Utrecht / Utrecht University [Utrecht]
2 Soft Condensed Matter

We study crystal nucleation in a binary mixture of hard spheres and investigate the composition and size of the (non)critical clusters using Monte Carlo simulations. In order to study nucleation of a crystal phase in computer simulations, a one-dimensional order parameter is usually defined to identify the solid phase from the supersaturated fluid phase. We show that the choice of order parameter can strongly influence the composition of noncritical clusters due to the projection of the Gibbs free-energy landscape in the two-dimensional composition plane onto a one-dimensional order parameter. We investigate the effect of the order parameter on the cluster composition for nucleation of a substitutional solid solution in a simple toy model of identical hard spheres but tagged with different colors and for nucleation of an interstitial solid solution in a binary hard-sphere mixture with a diameter ratio q = 0.3. In both cases, we find that the composition of noncritical clusters depends on the order parameter choice, but are well explained by the predictions from classical nucleation theory. More importantly, we find that the barrier height and critical cluster do not depend on the order parameter choice.

Mots clés: Physical Sciences

Domaines: Matière Condensée [cond-mat]

Ran Ni, Frank Smallenburg, Laura Filion, Marjolein Dijkstra. Crystal Nucleation in binary hard-sphere mixtures: The effect of order parameter on the cluster composition. Molecular Physics, 2011, 109 (07-10), pp.1213-1227. ⟨10.1080/00268976.2011.554333⟩. ⟨hal-00692121⟩