Berlin 2012 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 32: Soft Matter II

DY 32.8: Vortrag

Freitag, 30. März 2012, 11:45–12:00, MA 144

Freezing behavior of parallel hard spherocubes — Matthieu Marechal, •Urs Zimmermann, and Hartmut Löwen — Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätstraße 1, 40225 Düsseldorf, Germany

The monocomponent fluid of parallel hard cubes exhibits a continuous freezing transition, whereas hard spheres possess a first order freezing transition. We introduce the model of parallel hard spherocubes, a class of colloidal shapes characterized by the cube parameter q that describes the continuous deformation from parallel hard cubes (q=1) to hard spheres (q=0). The extended-deconvolution fundamental measure theory is used as well as Monte Carlo and event-driven Molecular Dynamics simulations to determine the phase boundaries. The qualitative change from continuous freezing to first order freezing is analyzed with respect to the shape of the spherocubes. The continuous freezing is found to be persistence for cubes with finite rounding (q<1). We present a phase diagram of packing fraction and the cube parameter q, discuss deviations between theory and simulations and observe an anomalous high vacancy concentration (>10%) in the solid phase. Furthermore a new stable crystalline structure corresponding to a sheared simple cubic phase is found.