8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P8.24Thu 811:10-14:00Bond order in hard sphere colloidal systems tracked bycoherent x-raysFelix Lehmkühler, 1 Christian Gutt, 1 Peter Wochner, 2 Birgit Fischer, 1 HeikoConrad, 1 Miguel Catro-Colin, 2 Sooheyong Lee, 3 Ingo Steinke, 1 MichaelSprung, 1 Diling Zhu, 3 Henrik Lemke, 3 Stephanie Bogle, 2 Paul Fuoss, 4 G. BrianStephenson, 4 and Marco Cammarata 31 DESY, Notkestr. 85, 22607, Hamburg, Germany2 Max-Planck-Institut für Intelligente Systeme, Stuttgart, Germany3 SLAC National Accelerator Laboratory, Menlo Park, United States of America4 Argonne National Laboratory, Argonne, United States of AmericaUnderstanding the structure of liquids and glasses is one of the holy grails in condensed matterphysics. However, the search for structural order is complicated because the ensemble averagedstructure factors of liquids and glasses indicates the usual short range density-density correlationonly. MD simulations showed that liquids develop a structural bond-order on local scale.Bond-order in glasses may remain from underlying crystallization processes or is suppressedby geometrical frustration via local symmetries, not extendable in 3D. We showed recently thatx-ray speckle patterns from colloidal glasses exhibit pronounced angular correlations [1]. Herewe will show how to extract the bond order parameters from speckle patterns of hard spherecolloidal suspensions. Due to the fast relaxation times, ultra-short x-ray pulses provided by thex-ray free electron laser LCLS were used to study the fluid phase, while coherent x-ray scatteringexperiments were performed at PETRAIII for the glass. Our results show that bond-ordering inhard sphere systems exists with dominating symmetry that can be connected to an underlyingcubic or hexagonal structure. Since also higher order bond-order parameters are observed, theidea of geometrical frustration within the system is supported. For the glass phase the bond ordercan be correlated with the relaxation times indicating that the slowing down of the dynamics atthe glass transition is caused by an onset of bond-ordering in the supercooled liquid.[1] P. Wochner, C. Gutt et al. PNAS 106, 11511 (2009).24