Dynamics of a model colloidal suspension from dilute to freezing

Hannam, S. D. W.; Daivis, Peter J.; Bryant, Gary

doi:10.1103/physreve.94.012619

Cited by 7 publications

(21 citation statements)

References 58 publications

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“…We found that at finite wavevectors the intermediate scattering function could be modelled as a double exponential decay with e↵ective short-and long-time di↵usion coe cients [13]. This is in line with experimental analysis [17], though our definition of the short-time di↵usion coe cient di↵ers from the usual convention.…”

Section: Introductionsupporting

confidence: 85%

“…The explicit solvent was included in the model in an attempt to match the dynamics of a real colloidal suspension by having the larger particles di↵use through a solvent with a viscosity and inertia, rather than moving ballistically through a vacuum. However our attempt to include hydrodynamic interactions was only partially successful as the trend in the self di↵usion coe cients with packing fraction is qualitatively similar to that observed in Brownian dynamics simulations [13]. We calculated the intermediate scattering function (which is a key quantity measured in dynamic light scattering experiments [7,8,11,[14][15][16]) over a large range of packing fractions and wavevectors in order to systematically study the change in dynamics on the approach to the freezing point.…”

Section: Introductionmentioning

confidence: 93%

“…Therefore, Eq. (13) predicts that in the k ! 0 limit the decay of the colloidal particle intermediate scattering function will be the sum of two exponentials with decay rates proportional to di↵usion coe cients D ± that are calculated from a combination of the four bulk inter-di↵usion coe cients using Eq.…”

Section: B Macroscopic Di↵usive Limitmentioning

confidence: 99%

“…Usually it is defined as the zero time limit of the time dependent di↵usion coe cient, however this can be ambiguous and di cult to determine, so instead we isolated the two exponential decay modes to determine their individual amplitudes and decay coe cients, and related the shorttime di↵usion coe cient to the decay rate of the faster decaying mode. The conclusions drawn in [13] are unchanged if the zero time limit definition is used. However, the model studied did not include polydispersity, which is key to inhibiting crystallization and allowing a glass transition to occur.…”

Section: Introductionmentioning

confidence: 97%

“…In previous work, we studied a unimodal model colloidal suspension with an explicit solvent [12,13]. In this system the colloidal particles were modeled using a Weeks-Chandler-Anderson (WCA) potential that was modified to include a hard-core, while the solvent was modeled using a simple WCA potential.…”

Section: Introductionmentioning

confidence: 99%

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Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

2017

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Molecular dynamics simulation was used to study a model colloidal suspension with two species of slightly different sized colloidal particles in an explicit solvent. In this work we calculated the four interdiffusion coefficients for the ternary system, which were then used to calculate the decay coefficients D_{±} of the two independent diffusive modes. We found that the slower D_{-} decay mode, which is associated with the system's ability to undergo compositional changes, was responsible for the long-time decay in the intermediate scattering function. We also found that a decrease in D_{-} to negligible values at a packing fraction of Φ_{g}=0.592 resulted in an extreme slow-down in the long-time decay of the intermediate scattering function often associated with the glass transition. Above Φ_{g}, the system formed a long-lived metastable state that did not relax to its equilibrium crystal state within the simulation time window. We concluded that the inhibition of crystallization was caused by the inability of the quenched fluid to undergo the compositional changes needed for the formation of the equilibrium crystal.

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Section: Introductionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 93%

Section: B Macroscopic Di↵usive Limitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

2017

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Nonequilibrium Molecular Dynamics

Todd

Daivis

2017

124

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Written by two specialists with over twenty-five years of experience in the field, this valuable text presents a wide range of topics within the growing field of nonequilibrium molecular dynamics (NEMD). It introduces theories which are fundamental to the field - namely, nonequilibrium statistical mechanics and nonequilibrium thermodynamics - and provides state-of-the-art algorithms and advice for designing reliable NEMD code, as well as examining applications for both atomic and molecular fluids. It discusses homogenous and inhomogenous flows and pays considerable attention to highly confined fluids, such as nanofluidics. In addition to statistical mechanics and thermodynamics, the book covers the themes of temperature and thermodynamic fluxes and their computation, the theory and algorithms for homogenous shear and elongational flows, response theory and its applications, heat and mass transport algorithms, applications in molecular rheology, highly confined fluids (nanofluidics), the phenomenon of slip and how to compute it from basic microscopic principles, and generalized hydrodynamics.

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Non-Gaussian, transiently anomalous and ergodic self-diffusion of flexible dumbbells in crowded two-dimensional environments: coupled translational and rotational motions

Klett

Cherstvy

Shin

et al. 2021

Preprint

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We employ Langevin-dynamics simulations to unveil non-Brownian and non-Gaussian center-of-mass self-diffusion of massive flexible dumbbell-shaped particles in crowded two-dimensional solutions. We also study the intra-dumbbell dynamics due to the relative motion of the two constituent elastically-coupled disks. Our main focus is on effects of the crowding fraction φ and the particle structure on the diffusion characteristics. We evaluate the time-averaged mean-squared displacement (TAMSD), the displacement probability-density function (PDF) and the displacement autocorrelation function (ACF) of the dimers. For the TAMSD at highly crowded conditions of dumbbells, e.g., we observe a transition from the short-time ballistic behavior, via an intermediate subdiffusive regime, to long-time Brownian-like spreading dynamics. The crowded system of dimers exhibits two distinct diffusion regimes distinguished by the scaling exponent of the TAMSD, the dependence of the diffusivity on φ, and the features of the displacement-ACF. We attribute these regimes to a crowding-induced transition from a viscous to a viscoelastic diffusion medium upon growing φ. We also analyze the relative motion in the dimers, finding that larger φ suppress their vibrations and yield strongly non-Gaussian PDFs of rotational displacements. For the diffusion coefficients D(φ) of translational and rotational motion of the dumbbells an exponential decay with φ for weak and a power-law D(φ) ∝ (φ - φ*)2.4 for strong crowding is found. A comparison of simulation results with theoretical predictions for D(φ) is discussed and some relevant experimental systems are overviewed.

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Dynamics of a model colloidal suspension from dilute to freezing

Cited by 7 publications

References 58 publications

Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

Dramatic slowing of compositional relaxations in the approach to the glass transition for a bimodal colloidal suspension

Nonequilibrium Molecular Dynamics

Non-Gaussian, transiently anomalous and ergodic self-diffusion of flexible dumbbells in crowded two-dimensional environments: coupled translational and rotational motions

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