Mobility and diffusion of a tagged particle in a driven colloidal suspension

Lander, Boris; Seifert, Udo; Speck, Thomas

doi:10.1209/0295-5075/92/58001

Cited by 12 publications

(12 citation statements)

References 38 publications

(63 reference statements)

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“…At this density, the solidification process is limited by the rate with which additional particles “attach” (there are no direct attractive forces but arranging into ordered structures locally increases the entropy). Shear flow increases the diffusion both parallel and perpendicular to the direction of the shear flow 30 , and thus speeds up the attachment while the barrier to nucleate small solid clusters is still small. However, we observe that increasing the mean crystallization time reaches a minimum before it again increases for higher strain rates.…”

Section: Resultsmentioning

confidence: 99%

The role of shear in crystallization kinetics: From suppression to enhancement

Richard

Speck

2015

Sci Rep

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In many technical applications crystallization proceeds in the presence of stresses and flows, hence the importance to understand the crystallization mechanism in simple situations. We employ molecular dynamics simulations to study the crystallization kinetics of a nearly hard sphere liquid that is weakly sheared. We demonstrate that shear flow both enhances and suppresses the crystallization kinetics of hard spheres. The effect of shear depends on the quiescent mechanism: suppression in the activated regime and enhancement in the diffusion-limited regime for small strain rates. At higher strain rates crystallization again becomes an activated process even at densities close to the glass transition.

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Section: Resultsmentioning

confidence: 99%

The role of shear in crystallization kinetics: From suppression to enhancement

Richard

Speck

2015

Sci Rep

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“…The equilibrium condition of the η−bath has given rise to (1) the systematic (mean) force being derived from the free energy F , and (2) diffusion constant and mobility can be and in general will be violated; see e.g. [26,[34][35][36][37].…”

Section: Example: Steadily Driven Probementioning

confidence: 99%

The modified Langevin description for probes in a nonlinear medium

Krüger

Maes

2016

J. Phys.: Condens. Matter

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When the motion of a probe strongly disturbs the thermal equilibrium of the solvent or bath, the nonlinear response of the latter must enter the probe's effective evolution equation. We derive that induced stochastic dynamics using second order response around the bath thermal equilibrium. We discuss the nature of the new term in the evolution equation which is no longer purely dissipative, and the appearance of a novel time-scale for the probe related to changes in the dynamical activity of the bath. A major application for the obtained nonlinear generalized Langevin equation is in the study of colloid motion in a visco-elastic medium.

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“…proportional to the νth power of the velocity difference δ v i = v i − v flow between the particle velocity v i and the flow velocity v flow ( r i ) = e xγ y, whose fluctuations are neglected [20][21][22][23]. The flow can be viewed as being set up by a non-Newtonian fluid characterized by a friction coefficient ζ.…”

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confidence: 99%

Shear Flow of Non-Brownian Suspensions Close to Jamming

2012

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The dynamical mechanisms controlling the rheology of dense suspensions close to jamming are investigated numerically, using simplified models for the relevant dissipative forces. We show that the velocity fluctuations control the dissipation rate and therefore the effective viscosity of the suspension. These fluctuations are similar in quasi-static simulations and for finite strain rate calculations with various damping schemes. We conclude that the statistical properties of grain trajectories -in particular the critical exponent of velocity fluctuations with respect to volume fraction φ -only weakly depend on the dissipation mechanism. Rather they are determined by steric effects, which are the main driving forces in the quasistatic simulations. The critical exponent of the suspension viscosity with respect to φ can then be deduced, and is consistent with experimental data. It is generally assumed that QS accurately describe the dynamics of the true system in the limit of asymptotically small shear rateγ. However, the existence of a proper quasistatic limit remains controversial, and there is growing evidence that quasistatic flows actually correspond to a finite-size dominated regime, with a correlation length that saturates at the system size [8,14].Symmetrically, for φ < φ c , amorphous materials can flow under an infinitesimal shear stress σ and present a viscosity η diverging at φ c like η ∝ (φ c − φ) −α . Scaling laws are expected to be different in thermal (glassy) systems and in athermal sytems [16]. In the case of a suspension of non-Brownian particles, the best fit of recent experimental results give a critical exponent of α = 2.4 for volume-controlled experiments [15] and of α = 1.9 for pressure-controlled experiments [3]. The explanation of 1 (labelled ν = 1) or by the lubrication like mechanism of Eq. 3 (labelled LF). In MD, the viscosity is measured in the low shear rate regime, forγ = 10 −6 and ζ = 10 −1 . In this regime, η/ζ does not depend on the precise value of these parameters, as shown in Fig. 2a. The quantitative agreement between MD(ν = 1) and MD(LF) is coincidental. Inset: compilation of experimental data available in the literature at imposed pressure P (with φc = 0.587) and imposed volume fraction φ (with φc = 0.615) for the ratio of suspension to solvent viscosity.

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Mobility and diffusion of a tagged particle in a driven colloidal suspension

Cited by 12 publications

References 38 publications

The role of shear in crystallization kinetics: From suppression to enhancement

The role of shear in crystallization kinetics: From suppression to enhancement

The modified Langevin description for probes in a nonlinear medium

Shear Flow of Non-Brownian Suspensions Close to Jamming

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