(420ak) Self Assembly in of Soft Particle Fluids, and Hard-Soft Particle Mixtures

Soft, penetrable particles exhibit highly anomalous clustering behavior.  We present a study of these systems using integral equation theory, and predict a striking contact to overlap transition.  In the contact regime, the structure is that of a 'normal' fluid, while the overlap regime is characterized by entropy enhancement through cluster formation.  These clusters are formed due to multiple overlaps of purely repulsive particles.  At very large volume fractions, a cluster-crystal phase is predicted.  Both transitions are a function of the density of soft particles, their stiffness, and their penetrability.  While cluster size is independent of volume fraction, cluster density grows linearly with it.  Anomalous structure factors are predicted in both the overlap, and the cluster-crystal regimes. At very low temperatures, we predict ordered structures similar to charged colloidal crystals, having large lattice constants.  These lattice constants vary with the stiffness of the inter-particle potential.  We also present some initial results of hard and soft particle mixtures.  In these systems, the cluster-crystal phase is largely destroyed.  However, under certain conditions, the hard particles are encapsulated by soft particles.  This encapsulation is a function of the particle densities, and hence is highly tunable.