title: Hard spheres: crystallization and glass formation.
abstract: Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s>0.07. For 0.02<s<0.07, we find that increasing the polydispersity at a given concentration slows down crystal nucleation. The main effect here is that polydispersity reduces the supersaturation since it tends to stabilize the fluid but to destabilize the crystal. At a given polydispersity (<0.07), we find three regimes of nucleation: standard nucleation and growth at concentrations in and slightly above the coexistence region; 'spinodal nucleation', where the free-energy barrier to nucleation appears to be negligible, at intermediate concentrations; and, at the highest concentrations, a new mechanism, still to be fully understood, which only requires small rearrangement of the particle positions. The cross-over between the second and third regimes occurs at a concentration, approximately 58 per cent by volume, where the colloid experiments show a marked change in the nature of the crystals formed and the particle dynamics indicate an 'ideal' glass transition.
authors.affiliation: SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK. p.n.pusey@ed.ac.uk
authors.forename: P N
authors.initials: PN
authors.lastname: Pusey
authors.forename: E
authors.initials: E
authors.lastname: Zaccarelli
authors.forename: C
authors.initials: C
authors.lastname: Valeriani
authors.forename: E
authors.initials: E
authors.lastname: Sanz
authors.forename: Wilson C K
authors.initials: WC
authors.lastname: Poon
authors.forename: Michael E
authors.initials: ME
authors.lastname: Cates