The race to the bottom: approaching the ideal glass?

Royall, C. Patrick; Turci, Francesco; Tatsumi, Soichi; Russo, John; Robinson, Joshua F.

doi:10.1088/1361-648x/aad10a

Cited by 49 publications

(70 citation statements)

References 264 publications

(539 reference statements)

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“…Thus, extending configurational entropy measurements to even lower temperatures remains an important research goal. 60 As emphasized repeatedly, a negative S exc is not prohibited by thermodynamic laws. 56 This is also not 'unthinkable' since entropy is not a general measure of disorder.…”

Section: B Why the Configurational Entropy?mentioning

confidence: 95%

Configurational entropy of glass-forming liquids

Berthier

Ozawa

Scalliet

2019

The Journal of Chemical Physics

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The configurational entropy is one of the most important thermodynamic quantities characterizing supercooled liquids approaching the glass transition. Despite decades of experimental, theoretical, and computational investigation, a widely accepted definition of the configurational entropy is missing, its quantitative characterization remains fraud with difficulties, misconceptions and paradoxes, and its physical relevance is vividly debated. Motivated by recent computational progress, we offer a pedagogical perspective on the configurational entropy in glass-forming liquids. We first explain why the configurational entropy has become a key quantity to describe glassy materials, from early empirical observations to modern theoretical treatments. We explain why practical measurements necessarily require approximations that make its physical interpretation delicate. We then demonstrate that computer simulations have become an invaluable tool to obtain precise, non-ambiguous, and experimentally-relevant measurements of the configurational entropy. We describe a panel of available computational tools, offering for each method a critical discussion. This perspective should be useful to both experimentalists and theoreticians interested in glassy materials and complex systems. I. CONFIGURATIONAL ENTROPY AND GLASS FORMATION A. The glass transitionWhen a liquid is cooled, it can either form a crystal or avoid crystallization and become a supercooled liquid. In the latter case, the liquid remains structurally disordered, but its relaxation time increases so fast that there exists a temperature, called the glass temperature T g , below which structural relaxation takes such a long time that it becomes impossible to observe. The liquid is then trapped virtually forever in one of many possible structurally disordered states: this is the basic phenomenology of the glass transition. 1-4 Clearly, T g depends on the measurement timescale and shifts to lower temperatures for longer observation times. The experimental glass transition is not a genuine phase transition, as it is not defined independently of the observer.The rich phenomenology characterizing the approach to the glass transition has given rise to a thick literature. It is not our goal to review it, and we refer instead to previous articles. 1-9 There are convincing indications that the dynamic slowing down of supercooled liquids is accompanied by an increasingly collective relaxation dynamics. This is seen directly by the measurement of growing lengthscales for these dynamic heterogeneities, 10-12 or more indirectly by the growth of the apparent activation energy for structural relaxation, as seen in its non-Arrhenius temperature dependence. These observations suggest an interpretation of the experimental glass transition in terms of a generic, collective mechanism possibly controlled by a sharp phase transition. 13 'Solving the glass problem' thus amounts to identifying and obtaining direct experimental signatures about the fundamental nature and the mathematical des...

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Section: B Why the Configurational Entropy?mentioning

confidence: 95%

Configurational entropy of glass-forming liquids

Berthier

Ozawa

Scalliet

2019

The Journal of Chemical Physics

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“…The experimental window is therefore the appropriate regime to test the predictions made by the RFOT theory. Notice that in this paper, we neither try to go below T g , nor to examine the fate of supercooled liquids at even lower temperature [61].…”

Section: Relaxation Timesmentioning

confidence: 99%

Does the Adam-Gibbs relation hold in simulated supercooled liquids?

Ozawa

Scalliet

Ninarello³

et al. 2019

The Journal of Chemical Physics

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We perform stringent tests of thermodynamic theories of the glass transition over the experimentally relevant temperature regime for several simulated glass-formers. The swap Monte Carlo algorithm is used to estimate the configurational entropy and static point-to-set lengthscale, and careful extrapolations are used for the relaxation times. We first quantify the relation between configurational entropy and the point-to-set lengthscale in two and three dimensions. We then show that the Adam-Gibbs relation is generally violated in simulated models for the experimentally relevant time window. Collecting experimental data for several supercooled molecular liquids, we show that the same trends are observed experimentally. Deviations from the Adam-Gibbs relation remain compatible with random first order transition theory, and may account for the reported discrepancies between Kauzmann and Vogel-Fulcher-Tammann temperatures. Alternatively, they may also indicate that even near Tg thermodynamics is not the only driving force for slow dynamics.

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“…The glass transition remains the grand challenge of the condensed matter physics and material engineering (Kennedy, 2005;Berthier and Ediger, 2016;Kremer and Loidl, 2018;Royall et al, 2018;Tong and Tanaka, 2018). Decades of research yielded the excellent experimental and theoretical evidence, based on increasingly sophisticated approaches (Donth, 2007;Berthier and Ediger, 2016;Kremer and Loidl, 2018;Royall et al, 2018;Tong and Tanaka, 2018). However, the long-awaited cognitive breakthrough is still elusive.…”

Section: Introductionmentioning

confidence: 99%

“…However, the long-awaited cognitive breakthrough is still elusive. Notable problems appear even for the hallmark feature of the previtreous dynamics: the super-Arrhenius (SA) evolution of viscosity η (T) or the structural (primary, alpha) relaxation time τ (T) (Ngai, 2011;Berthier and Ediger, 2016;Kremer and Loidl, 2018;Royall et al, 2018;Tong and Tanaka, 2018). The general SA relation has the following form (Donth, 2007;Ngai, 2011):…”

Section: Introductionmentioning

confidence: 99%

“…Previtreous temperature changes of τ (T) or η (T) are inherently associated with the "Angell plot, " recognized as the hallmark picture for the glass transition physics (Angell, 1985;Böhmer et al, 1993;Donth, 2007;Ngai, 2011;Berthier and Ediger, 2016;Kremer and Loidl, 2018;Royall et al, 2018;Tong and Tanaka, 2018). It enables the common presentation of the previtreous dynamics for different glass formers via the normalized plot log 10 τ (T) or log 10 η (T) vs. T g /T , assuming τ T g = 10 2 s or η T g = 10 13 Poise (Angell, 1985;Böhmer et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

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Pressure-Related Universal Previtreous Behavior of the Structural Relaxation Time and Apparent Fragility

Drozd-Rzoska

2019

Front. Mater.

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The report presents the evidence for the hypothetically "universal" previtreous behavior of the pressure related apparent fragility: m T (P) ∞1/ (P * − P), where P * is the extrapolated singular pressure. This finding was the basis for deriving the "model-free" dependence for the pressure evolution of the structural relaxation time: τ (P) = τ P o (P * − P) −. All these led to the new way of testing the dynamic crossover phenomenon via 1/m T (P) vs. P plot. Finally, the behavior of electric conductivity in the previtreous domain is discussed. The experimental evidence covers 8 * OCB (liquid crystal), EPON 828 (resin), diisobutyl phthalate, and propylene carbonate (low molecular weight liquids). Experiments were carried up to extreme P∼ 2.2 GPa, in the "bulk" measurement capacitor. This report also contains a summary of existing descriptions of the pressure evolution of structural relaxation time or viscosity on approaching the glass transition.

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The race to the bottom: approaching the ideal glass?

Cited by 49 publications

References 264 publications

Configurational entropy of glass-forming liquids

Configurational entropy of glass-forming liquids

Does the Adam-Gibbs relation hold in simulated supercooled liquids?

Pressure-Related Universal Previtreous Behavior of the Structural Relaxation Time and Apparent Fragility

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