(109b) How Short-Range Attractions Impact The Structural Order, Self-Diffusivity, And Viscosity Of A Fluid

Suspended colloids exhibit a number of behaviors that are similar to those of individual molecules or atoms of a pure liquid. Colloids are interesting model systems for the latter because they are both large and slow enough to allow direct experimental measurement of their real-space structure and dynamics. However, the attractive interactions between colloids, unlike those between atoms or molecules, can be tuned to be short-ranged relative to the particle diameter, which in turn leads to anomalous structural, thermodynamic, and dynamical trends [1]. In this talk, we present comprehensive simulations results for the self-diffusivity, viscosity, and the local structural order of a model fluid with short-range attractions in both its equilibrium and supercooled states [2]. We show how the transport properties of this fluid can be quantitatively related to its static structure. We also demonstrate that, similar to liquid water [3], the model fluid exhibits a region of dynamic anomalies on its phase diagram that is a subset of a larger set of conditions where it displays structural anomalies. Lastly, we show that the breakdown of the Stokes-Einstein relationship approaching either the ?repulsive? or ?attractive? glass transition occurs for conditions where viscosity and self-diffusivity develop different couplings to the degree of pair-wise structural order of the fluid, reflecting the onset of dynamic heterogeneities.

[1] F Sciortino, Nature Materials, 1, 145, (2002). [2] W. P. Krekelberg, J. Mittal, V. Ganesan, and T. M. Truskett, arXiv:0705.0381v1 (2007). [3] J. R. Errington, P. G. Debenedetti, Nature, 409, 318, (2001).