How short-range attractions impact the structural order, self-diffusivity, and viscosity of a fluid.
We present molecular simulation data for viscosity, self-diffusivity, and the local structural ordering of (i) a hard-sphere fluid and (ii) a square-well fluid with short-range attractions. The latter fluid exhibits a region of dynamic anomalies in its phase diagram, where its mobility increases upon isochoric cooling, which is found to be a subset of a larger region of structural anomalies, in which its pair correlations strengthen upon isochoric heating. This "cascade of anomalies" qualitatively resembles that found in recent simulations of liquid water. The results for the hard-sphere and square-well systems also show that the breakdown of the Stokes-Einstein relation upon supercooling occurs for conditions where viscosity and self-diffusivity develop different couplings to the degree of pairwise structural ordering of the liquid. We discuss how these couplings reflect dynamic heterogeneities. Finally, we note that the simulation data suggest how repulsive and attractive glasses may generally be characterized by two distinct levels of short-range structural order.
Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA. krekel@che.utexas.edu
William P
WP
Krekelberg
Jeetain
J
Mittal
Venkat
V
Ganesan
Thomas M
TM
Truskett
D003102:Colloids / Q000737:chemistry*; D045424:Complex Mixtures / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
D003102:Colloids; D045424:Complex Mixtures; D014867:Water