From Close-Packed to Topologically Close-Packed: Formation of Laves Phases in Moderately Polydisperse Hard-Sphere Mixtures

TL;DR

This study uses computer simulations to show that increased particle size polydispersity in hard-sphere mixtures leads to size-based fractionation and the formation of topologically close-packed Laves phases alongside disordered phases.

Contribution

It demonstrates that higher polydispersity promotes the formation of Laves phases in hard-sphere mixtures, extending understanding of phase behavior in polydisperse systems.

Findings

Polydispersity induces size-based fractionation.

Laves phases form with increased polydispersity.

Results are consistent across different size distributions.

Abstract

Particle size polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased polydispersity fractionate on the basis of particle size, and a bimodal subpopulation favors formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.