Formation of Polymorphic Cluster Phases for Purely Repulsive Soft Spheres

TL;DR

This paper combines density functional theory and simulations to predict first-order freezing into cluster crystals in ultrasoft spheres, revealing density-independent lattice constants and polymorphic transitions between bcc and fcc phases.

Contribution

It provides the first unambiguous theoretical and simulation evidence for clustering and polymorphic phase transitions in purely repulsive ultrasoft particle systems.

Findings

First-order freezing into cluster crystals predicted.

Clusters consist of overlapping particles with density-independent lattice constants.

Polymorphic bcc-fcc transitions observed, with fcc stable at high densities.

Abstract

We present results from density functional theory and computer simulations that unambiguously predict the occurrence of first-order freezing transitions for a large class of ultrasoft model systems into cluster crystals. The clusters consist of fully overlapping particles and arise without the existence of attractive forces. The number of particles participating in a cluster scales linearly with density, therefore the crystals feature density-independent lattice constants. Clustering is accompanied by polymorphic bcc-fcc transitions, with fcc being the stable phase at high densities.