Regensburg 2007 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Colloids and Nanoparticles I: Structure

CPP 3.3: Vortrag

Montag, 26. März 2007, 10:30–10:45, H47

Novel crystal phase in suspensions of hard ellipsoids — •Patrick Pfleiderer and Tanja Schilling — Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55099 Mainz

Hard ellipsoids serve as a popular model system for granular materials, and colloidal and molecular liquids, solids, and glasses. We present a Monte Carlo simulation study on the crystalline phases of hard ellipsoids of revolution. For aspect ratios ≥ 3 we have found a novel crystal, which replaces the previously suggested stretched-fcc phase [D. Frenkel and B. M. Mulder, Mol. Phys. 55, 1171 (1985)]. The unit cell of the new solid contains two ellipsoids with unequal orientations. The lattice is simple monoclinic. The crystal possesses a rheological specialty: The angle of inclination of the lattice, β, is a very soft degree of freedom, while the two right angles are stiff. Further, we have determined that for one particular value of β, the close-packed version of this crystal is a specimen of the family of superdense packings recently reported [A. Donev et al., Phys. Rev. Lett. 92, 255506 (2004)]. Our update of the phase diagram is relevant for studies of nucleation and glassy dynamics of colloidal suspensions of ellipsoids; the rheology may inspire new materials with tailor-made properties.