Dynamical Heterogeneity and Jamming in Glass-Forming Liquids

Lacevic, Naida; Glotzer, Sharon C.

doi:10.1021/jp040401r

Cited by 27 publications

(20 citation statements)

References 80 publications

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“…As follows from the figure, these distributions are close to exponentials, as expected according to Ref. [78][79][80][81][82]. Figure 4(a) shows "the total" ASCFs (6) for the systems with (L/2) = 9.41 and (L/2) = 21.38 at time t = 0.…”

Section: A the Average Correlation Functionssupporting

confidence: 78%

Green-Kubo stress correlation function at the atomic scale and a long-range bond-orientational ordering in a model liquid

Levashov

2018

Phys. Rev. E

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Recently there have been several considerations by different authors of viscosity and the Green-Kubo stress correlation function from the microscopic perspective. In most of these and earlier works the atomic level stress is the minimal element of stress. It is also possible to consider, for pairwise interaction potentials, as the minimal elements of stress, the stress tensors associated with the pairs of interacting particles. From this perspective, the atomic level stress is not the minimal stress element, but a sum of all pair stress elements in which involved a selected particle. In this paper, we consider the Green-Kubo stress correlation function from a microscopic perspective using the stress tensors of interacting pairs as the basic stress elements. The obtained results show the presence of a long-range bond-orientational order in the studied model liquid and naturally elucidate the connection of the bond-orientational order with viscosity. It turns out that the longrange bond-orientational order is more clearly expressed in the pairs' stress correlation function than in the atomic stress correlation function. On the other hand, previously observed stress waves are much better expressed in the atomic stress correlation functions. We also address the close connection of our approach with the previous bond-orientational order considerations. Finally, we consider the probability distributions for the bond-stress and atomic stress correlation products at selected distances. The character of the obtained probability distributions raises questions about the meaning of the average correlation functions at large distances.

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Section: A the Average Correlation Functionssupporting

confidence: 78%

Green-Kubo stress correlation function at the atomic scale and a long-range bond-orientational ordering in a model liquid

Levashov

2018

Phys. Rev. E

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“…In order to characterize the spatially heterogeneous dynamics [38,41,42] one usually resorts to a four-point time-dependent density correlation function and to its fluctuations (susceptibility). This latter measures the correlated motion between pairs of particles.…”

Section: Spatial Heterogeneous Dynamicsmentioning

confidence: 99%

Granular packs under vertical tapping: Structure evolution, grain motion, and dynamical heterogeneities

2007

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The compaction dynamics of a granular media subject to a sequence of vertical taps made of fluid pulses is investigated via molecular dynamics simulations. Our study focuses on three different levels: macroscopic (volume fraction), mesoscopic (Voronoï volumes, force distributions), and microscopic (grain displacements). We show that the compaction process has many characteristics which are reminiscent of the slow dynamics of glass forming systems, as previously suggested. For instance, the mean volume fraction slowly increases in time and approaches a stationary value following a stretched exponential law, and the associated compaction time diverges as the tapping intensity decreases. The study of microscopic quantities also put in evidence the existence of analogies with the dynamics of glass formers, as the existence of dynamical heterogeneities and spatially correlated motion of grains; however, it also shows that there are important qualitative differences, as, for instance, in the role of the cage effect. Correlations between geometry and dynamics of the system at the grain level are put in evidence by comparing a particle Voronoï volume and its displacement in a single tap.

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“…We predict a correlation of the ratio of the dynamical crossover temperature to the laboratory glass transition temperature, and the heat capacity discontinuity at the glass transition, ∆Cp. The predicted correlation agrees with experimental results for the 21 materials compiled by Novikov and Sokolov. Our increased ability to visualize and experimentally probe supercooled liquids on the nanometer length scale has explicitly revealed the presence of cooperatively rearranging regions 1, 2,3,4,5,6,7,8,9,10 (CRR's). The cooperative rearrangement of groups of many molecules has long been thought to underlie the dramatic slowing of liquid dynamics upon cooling and could also explain the non-exponential time dependence of relaxation in glassy liquids.…”

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confidence: 99%

The shapes of cooperatively rearranging regions in glass-forming liquids

2006

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The shapes of cooperatively rearranging regions in glassy liquids change from being compact at low temperatures to fractal or "stringy" as the dynamical crossover temperature from activated to collisional transport is approached from below. We present a quantitative microscopic treatment of this change of morphology within the framework of the random first order transition theory of glasses. We predict a correlation of the ratio of the dynamical crossover temperature to the laboratory glass transition temperature, and the heat capacity discontinuity at the glass transition, ∆Cp. The predicted correlation agrees with experimental results for the 21 materials compiled by Novikov and Sokolov.Our increased ability to visualize and experimentally probe supercooled liquids on the nanometer length scale has explicitly revealed the presence of cooperatively rearranging regions 1,2,3,4,5,6,7,8,9,10 (CRR's). The cooperative rearrangement of groups of many molecules has long been thought to underlie the dramatic slowing of liquid dynamics upon cooling and could also explain the non-exponential time dependence of relaxation in glassy liquids. Activated transitions of regions of growing size were postulated in the venerable Adam-Gibbs argument for the glass transition 11 . To move, a region, in the AG view, must have a minimum of two distinct conformational states. Natural as this suggestion is, the sizes predicted from literally applying this notion are far too small to explain laboratory observations. The minimal AG cluster would have only two particles since the measured entropy per particle is of order 1k B at the glass transition.A distinct approach, the random first order transition (RFOT) theory of glasses, is based on a secure statistical mechanical formulation at the mean field level 12,13,14,15,16,17,18,19 but also goes beyond mean field theory to explain the non-exponential, non-Arrhenius dynamics of supercooled liquids through the existence of compact, dynamically reconfiguring regions ("entropic droplets") 20,21,22 whose predicted size is, in contrast to the Adam-Gibbs bound, very much consistent with what has been measured (125-200 molecules), using both scanning microscopy 1,8 and NMR techniques 7,9 , at temperatures near to T g .Computer simulations 3,23,24 and light microscopy studies of colloidal glasses 10 , however, have revealed dynamically reconfiguring regions that are not compact and contain fewer particles. Some investigators describe these regions as "fractal 6 " while others use the term "strings 3 " to characterize them. It has been suggested that such "stringy" excitations should be taken as the fundamental objects in the theory of glass transitions. As we will show, the fractal nature of the dynamically reconfiguring regions in the relatively high temperature regime probed in current computer simulations follows naturally from RFOT theory. To be precise, RFOT theory predicts the shape of the reconfiguring regions changes from compact to fractal as the system is heated from low temperatures, chara...

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Dynamical Heterogeneity and Jamming in Glass-Forming Liquids

Cited by 27 publications

References 80 publications

Green-Kubo stress correlation function at the atomic scale and a long-range bond-orientational ordering in a model liquid

Green-Kubo stress correlation function at the atomic scale and a long-range bond-orientational ordering in a model liquid

Granular packs under vertical tapping: Structure evolution, grain motion, and dynamical heterogeneities

The shapes of cooperatively rearranging regions in glass-forming liquids

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