CiteULike: dchens function

The microrheology of colloidal dispersions

TGM van de Ven — 2008-04-29T20:01:00-00:00

Colloid & Polymer Science, Vol. 255, No. 8. (1977), pp. 794-804.

Summary A theory of doublet formation, the first step in coagulation of dilute monodisperse spherical sols subjected to shearing motion, in which Brownian motion dominates the effects of shear is presented. Contrary to Smoluchowski's predictions, it is found that the increase in the rate of coagulation due to shear is not proportional to the shear rateG, but toG1/2 with the proportionality constant depending on the perikinetic capture efficiency, the translational diffusion constant and sphere radius. With non-spherical particles the increase rate due to shear also varies with G1/2 and depends, in addition, on particle size and shape.

Search for a correlation length in a simulation of the glass transition

Richard Ernst — 2007-07-30T15:27:17-00:00

Physical Review B, Vol. 43, No. 10. (1 April 1991), 8070.

We have looked for evidence of a correlation length in a molecular-dynamics simulation of the glass transition. We have studied the correlation functions of both the translational order of particle positions and the orientational order of nearest-neighbor bond angles; and have seen no indication of a diverging length scale. We also present data from the simulation; which extend recent laboratory measurements of the frequency-dependent specific heat and thermal conductivity.

Green's function measurements of force transmission in 2D granular materials

Junfei Geng — 2008-03-28T13:14:35-00:00

Physica D: Nonlinear Phenomena, Vol. 182, No. 3-4. (15 August 2003), pp. 274-303.

We describe experiments that probe the response to a point force of 2D granular systems under a variety of conditions. Using photoelastic particles to determine forces at the grain scale, we obtain ensembles of responses for the following particle types, packing geometries and conditions: monodisperse ordered hexagonal packings of disks, bidisperse packings of disks with different amounts of disorder, disks packed in a regular rectangular lattice with different frictional properties, packings of pentagonal particles, systems with forces applied at an arbitrary angle at the surface, and systems prepared with shear deformation, hence with texture or anisotropy. We experimentally show that disorder, packing structure, friction and texture significantly affect the average force response in granular systems. For packings with weak disorder, the mean forces propagate primarily along lattice directions. The width of the response along these preferred directions grows with depth, increasingly so as the disorder of the system grows. Also, as the disorder increases, the two propagation directions of the mean force merge into a single direction. The response function for the mean force in the most strongly disordered system is quantitatively consistent with an elastic description for forces applied nearly normally to a surface, but this description is not as good for non-normal applied forces. These observations are consistent with recent predictions of Bouchaud et al. [Eur. Phys. J. E 4 (2001) 451] and Socolar et al. [Eur. Phys. J. E 7 (2002) 353] and with the anisotropic elasticity models of Goldenberg and Goldhirsch [Phys. Rev. Lett. 89 (2002) 084302]. At this time, it is not possible to distinguish between these two models. The data do not support a diffusive picture, as in the q-model, and they are in conflict with data by Da Silva and Rajchenbach [Nature 406 (2000) 708] that indicate a parabolic response for a system consisting of cuboidal blocks. We also explore the spatial properties of force chains in an anisotropic textured system created by a nearly uniform shear. This system is characterized by stress chains that are strongly oriented along an angle of 45[degree sign], corresponding to the compressive direction of the shear deformation. In this case, the spatial correlation function for force has a range of only one particle size in the direction transverse to the chains, and varies as a power law in the direction of the chains, with an exponent of -0.81. The response to forces is the strongest along the direction of the force chains, as expected. Forces applied in other directions are effectively refocused towards the strong force chain direction.

Direct Observation of Stretched-Exponential Relaxation in Low-Temperature Lennard-Jones Systems Using the Cage Correlation Function

Eran Rabani — 2008-03-24T22:16:42-00:00

Physical Review Letters, Vol. 82, No. 18. (3 May 1999), 3649.

We report on the direct observation of stretched exponential relaxation in low-temperature monatomic Lennard-Jones systems which were cooled slowly from the liquid phase to form crystals with a large number of defects. We use the cage correlation function [E. Rabani; J. D. Gezelter; and B. J. Berne; J. Chem. Phys. 107 ; 6867 (1997)] which measures changes in atomic surroundings to observe the stretched exponential relaxations. We obtain a distribution of hopping rates assuming that the origin of the Kohlrausch-Williams-Watts law is from static disorder in the distribution of barrier heights.

Quantifying spatially heterogeneous dynamics in computer simulations of glass-forming liquids

Sharon Glotzer — 2008-03-01T23:23:23-00:00

Journal of Physics: Condensed Matter, Vol. 11, No. 10A. (1999), pp. A285-A295.

We examine the phenomenon of dynamical heterogeneity in computer simulations of an equilibrium, glass-forming liquid. We describe several approaches for quantifying the spatial correlation of single-particle motion, and show that spatial correlations of particle displacements become increasingly long range as the temperature decreases toward the mode-coupling critical temperature.

Time-dependent, four-point density correlation function description of dynamical heterogeneity and decoupling in supercooled liquids

Sharon Glotzer — 2007-12-05T10:11:21-00:00

The Journal of Chemical Physics, Vol. 112, No. 2. (2000), pp. 509-512.

Spectral diffusion in liquids with fluctuating solvent responses: Dynamical heterogeneity and rate exchange

Ranko Richert — 2008-03-01T23:13:46-00:00

The Journal of Chemical Physics, Vol. 115, No. 3. (2001), pp. 1429-1434.

Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function

N Lacevic — 2008-03-01T17:49:06-00:00

J. Chem. Phys. 119, 7372 (2003)