Corresponding States of Structural Glass Formers. II

Elmatad, Yael S.; Chandler, David; Garrahan, Juan P.

doi:10.1021/jp1076438

Cited by 107 publications

(113 citation statements)

References 57 publications

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“…Table 2 shows the ratio of the mean T K to T g agrees quite well with (often imprecise) experimental estimates. The deduced ratios of T K /T vft also seem reasonable; recall that in experiment they are sometimes close to unity, but are known to show significant deviations in both directions for diverse materials [71,74]. We emphasize that in our approach there are no true divergences, so we ascribe no physical significance to the extrapolations.…”

Section: Entropy Crisis Perspectivesupporting

confidence: 61%

“…The former builds on a high temperature local activated event as the basic excitation, while the latter does not. In both cases, configurational entropy controls the barrier in the deeply supercooled regime leading to the classic VFT form (also motivated from very different "free volume" arguments [65]): Coarse-grained dynamic facilitation models based on directional mobility field propagation predict a "parabolic law" in the deeply supercooled regime [18,70,71]:…”

Section: A Modelsmentioning

confidence: 99%

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Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids

Mirigian

Schweizer

2014

The Journal of Chemical Physics

167

480

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Building on the elastically collective nonlinear Langevin equation theory developed for hard spheres in the preceding paper I, we propose and implement a quasi-universal theory for the alpha relaxation of thermal liquids based on mapping them to an effective hard sphere fluid via the dimensionless compressibility. The result is a zero adjustable parameter theory that can quantitatively address in a unified manner the alpha relaxation time over 14 or more decades. The theory has no singularities above zero Kelvin, and relaxation in the equilibrium low temperature limit is predicted to be of a roughly Arrhenius form. The two-barrier (local cage and long range collective elastic) description results in a rich dynamic behavior including apparent Arrhenius, narrow crossover and deeply supercooled regimes, and multiple characteristic or crossover times and temperatures of clear physical meaning. Application of the theory to nonpolar molecules, alcohols, rare gases and liquids metals is carried out. Overall, the agreement with experiment is quite good for the temperature dependence of the alpha time, plateau shear modulus and Boson-like peak frequency for van der Waals liquids, though less so for hydrogen-bonding molecules. The theory predicts multiple growing length scales upon cooling, which reflect distinct aspects of the coupled local hopping and cooperative elastic physics. Calculations of an activation volume that grows with cooling, which is correlated with a measure of dynamic cooperativity, agree quantitatively with experiment. Comparisons with elastic, entropy crisis, dynamic facilitation and other approaches are performed, and a fundamental basis for empirically-extracted crossover temperatures is established. The present work sets the stage for addressing distinctive glassy phenomena in polymer melts, and diverse liquids under strong confinement.

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Section: Entropy Crisis Perspectivesupporting

confidence: 61%

Section: A Modelsmentioning

confidence: 99%

Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids

Mirigian

Schweizer

2014

The Journal of Chemical Physics

167

480

View full text Add to dashboard Cite

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“…However, classic models 7,8 and some modern models 9 that predict such VFT-like behaviour have been challenged by new evidence from both theoretical [10][11][12][13][14] and experimental [15][16][17][18][19][20][21][22] works, which contradict such a finite temperature divergence. The difficulty of directly addressing the VFT behaviour experimentally arises owing to the 'geological' ages 23 required to attain equilibrium far below the glass transition temperature T g .…”

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confidence: 99%

Using 20-million-year-old amber to test the super-Arrhenius behaviour of glass-forming systems

2013

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Fossil amber offers the opportunity to investigate the dynamics of glass-forming materials far below the nominal glass transition temperature. This is important in the context of classical theory, as well as some new theories that challenge the idea of an 'ideal' glass transition. Here we report results from calorimetric and stress relaxation experiments using a 20-millionyear-old Dominican amber. By performing the stress relaxation experiments in a step-wise fashion, we measured the relaxation time at each temperature and, above the fictive temperature of this 20-million-year-old glass, this is an upper bound to the equilibrium relaxation time. The results deviate dramatically from the expectation of classical theory and are consistent with some modern ideas, in which the diverging timescale signature of complex fluids disappears below the glass transition temperature.

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“…[8]. The system is a liquid mixture at a temperature that is 80% below that of the onset temperature, T o [8][9][10][11][12], and the trajectory runs for an observation time t obs ≈ 10 τ . Here, τ stands for the equilibrium structural relaxation time.…”

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confidence: 99%

Using thesensemble to probe glasses formed by cooling and aging

2015

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From length scale distributions characterizing frozen amorphous domains, we relate the s-ensemble method with standard cooling and aging protocols for forming glass. We show that in a general class of models, where space-time scaling is in harmony with that of experiment, the domain size distributions obtained with the s-ensemble are identical to those obtained through cooling or aging, but the computational effort for applying the s-ensemble is generally many orders of magnitude smaller than that of straightforward numerical simulation of cooling or aging.Through biasing statistics of trajectory space, the socalled "s-ensemble" method, non-equilibrium phase transitions emerge between ergodic liquid-like states and dynamically inactive glass-like states. This class of transitions are found in idealized lattice models [1,2] and in simulations of atomistic models [3][4][5]. In the latter case, it affords a systematic computational means of preparing exceptionally stable glass-states states [6]. This Letter draws the conclusion that the s-ensemble transition coincides with the physical glass transition [7], and the ensemble of its inactive states are those of natural structural glass. Specifically, we derive correspondence between spatial correlations in the s-ensemble glass with those in the glass produced with finite-rate cooling or aging. The correspondence provides a basis for an extraordinarily efficient route for preparing structural glass with molecular simulations.Space-time structure of glass-forming liquids. To begin, it is helpful to consider Figs. 1a and 1b, which render trajectories of a two-dimensional 5 × 10 4 -particle system in a fashion that extends the approach of Ref. [8]. The system is a liquid mixture at a temperature that is 80% below that of the onset temperature, T o [8][9][10][11][12], and the trajectory runs for an observation time t obs ≈ 10 τ . Here, τ stands for the equilibrium structural relaxation time. It is about 10 5 integration steps at this particular temperature, and t obs , being 10 times longer, provides ample opportunity to observe the nature of dynamic heterogeneity in the system.Most motions in glass-forming liquids are irrelevant vibrations, and the amplitudes of most of those vibrations are similar in size to typical enduring displacements [8]. Irrelevant vibrations can be filtered out by focusing on inherent structures [13]. The set of particle positions at time t, {r i (t)}, evolves by molecular dynamics; the inherent structure, {r i (t)}, is the position of the potentialenergy minimum closest to {r i (t)}. The renderings in Fig. 1 refer to [a(r, t)] iso , whereHere, we take ∆t to be 10 3 integration steps, which is roughly the average time to complete an enduring displacement of one atomic diameter [8], and [· · · ] iso indicates iso-configurational averaging, which averages many trajectories of length ∆t, all starting from the same configuration [14]. Particles colored red in Fig. 1a are those for which the iso-configuration averagedr i (∆t) is more than 0.6 σ fromr ...

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Corresponding States of Structural Glass Formers. II

Cited by 107 publications

References 57 publications

Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids

Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids

Using 20-million-year-old amber to test the super-Arrhenius behaviour of glass-forming systems

Using thesensemble to probe glasses formed by cooling and aging

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