Light-scattering investigation of α and β relaxation near the liquid-glass transition of the molecular glass Salol

G, Li; Wm, Du; Sakai, Akira; Hz, Cummins

doi:10.1103/physreva.46.3343

Cited by 254 publications

(172 citation statements)

References 49 publications

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“…Thus, we know that the idealized MCT prediction breaks down at T = 278 K and below this temperature, its validity as such is unclear. However, when we fit the relaxation time to MCT expression (τ ∼ [(T −T fit c )/T fit c ] −γ ) we obtain a value, T fit c = 258 K, which is in excellent agreement with the experimental fits (6,8,9).…”

Section: Physicssupporting

confidence: 74%

“…T fit c is referred to as the MCT transition temperature. Above T fit c , MCT is found to explain many experimental results (6)(7)(8)(9), and below T fit c , the MCT picture of continuous diffusion fails eventually. It is conjectured that this breakdown is due to the ergodic to nonergodic transition in the dynamics and below T fit c activated dynamics becomes a dominant mode of transport.…”

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confidence: 93%

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Facilitation, complexity growth, mode coupling, and activated dynamics in supercooled liquids

Bhattacharyya

Bagchi

Wolynes

2008

Proc. Natl. Acad. Sci. U.S.A.

106

104

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In low-temperature-supercooled liquids, below the ideal modecoupling theory transition temperature, hopping and continuous diffusion are seen to coexist. Here, we present a theory that shows explicitly the interplay between the two processes and shows that activated hopping facilitates continuous diffusion in the otherwise frozen liquid. Several universal features arise from nonlinear interactions between the continuous diffusive dynamics [described here by the mode coupling theory (MCT)] and the activated hopping (described here by the random first-order transition theory). We apply the theory to a specific system, Salol, to show that the theory correctly predicts the temperature dependence of the nonexponential stretching parameter, β, and the primary α relaxation timescale, τ. The study explains why, even below the mean field ergodic to nonergodic transition, the dynamics is well described by MCT. The nonlinear coupling between the two dynamical processes modifies the relaxation behavior of the structural relaxation from what would be predicted by a theory with a complete static Gaussian barrier distribution in a manner that may be described as a facilitation effect. Furthermore, the theory correctly predicts the observed variation of the stretching exponent β with the fragility parameter, D. These two predictions also allow the complexity growth to be predicted, in good agreement with the results of Capaccioli et al. complexity | glass transition | random first order T he glass transition is characterized by a number of interesting kinetic phenomena. Very slow and simultaneously nonexponential relaxation of time correlation functions over large time windows is one such important phenomenon. This relaxation is often approximated by the stretched exponential, KohlrauschWilliam-Watts (KWW) formula, φ(t) = exp(−(t/τ )) β , with both β and τ exhibiting nontrivial temperature dependence. The origin of the stretching is usually attributed to the presence of dynamic heterogeneity in the system (1, 2). The temperature dependence of the typical relaxation time can be described by the the Vogel-where τ VFT is the high-temperature relaxation time, T o is the VFT temperature, and D is the fragility index. The fragility index, D, determines the degree of deviation from the Arrhenius law that is appropriate for simple activated events. Experimental and theoretical model studies have shown that β and D are correlated (3-5). The temperature dependence of τ has also been described by phenomenological mode coupling theory (MCT) expression,, but this ultimately breaks down at low temperature. T fit c is referred to as the MCT transition temperature. Above T fit c , MCT is found to explain many experimental results (6-9), and below T fit c , the MCT picture of continuous diffusion fails eventually. It is conjectured that this breakdown is due to the ergodic to nonergodic transition in the dynamics and below T fit c activated dynamics becomes a dominant mode of transport. However in an elegant work, Brumer and Reichman (10) (BR) ...

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Section: Physicssupporting

confidence: 74%

mentioning

confidence: 93%

Facilitation, complexity growth, mode coupling, and activated dynamics in supercooled liquids

Bhattacharyya

Bagchi

Wolynes

2008

Proc. Natl. Acad. Sci. U.S.A.

106

104

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“…The existence of a temperature T × , marking dynamical changes of fragile supercooled liquids below T M , has been already considered in the past (5,13,(36)(37)(38)(39)(40)(41)(42). This is due to problems such as the existence of the dynamical divergence associated with the VFT form and the possibility that neither T 0 nor T g is relevant to describe and understand slowing down in transport parameters of supercooled liquids.…”

mentioning

confidence: 99%

“…The conclusions of (40)(41)(42), the theoretical indication (9), together with the finding of cited works invocating the existence of a crossover temperature (5,13,(36)(37)(38)(39)(40)(41) propose that VFT must be reconsidered for the explanation of the dynamical arrest. We have examined the temperature behavior of the viscosity and the other transport coefficients of many liquids.…”

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confidence: 99%

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Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature

Mallamace

Branca

Corsaro

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

210

233

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It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T . In an Arrhenius plot, ln η vs 1∕T , a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel-Fulcher-Tammann law. Here we analyze existing data of the transport coefficients of 84 glassforming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η × , where η × has the same value, η × ≈ 10 3 Poise, for all 84 liquids. The crossover temperature, T × , located well above the calorimetric glass transition temperature T g , marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T × to Arrhenius behavior below T × . We also show that below T × the familiar Stokes-Einstein relation D∕T ∼ η −1 breaks down and is replaced by a fractional form D∕T ∼ η −ζ , with ζ ≈ 0.85. dynamical arrest | dynamic transition | supercooled liquids

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Dielectric Spectroscopy of Glassy Dynamics

Lunkenheimer

Köhler

Kastner

et al. 2012

Structural Glasses and Supercooled Liquids

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Light-scattering investigation of α and β relaxation near the liquid-glass transition of the molecular glass Salol

Cited by 254 publications

References 49 publications

Facilitation, complexity growth, mode coupling, and activated dynamics in supercooled liquids

Facilitation, complexity growth, mode coupling, and activated dynamics in supercooled liquids

Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature

Dielectric Spectroscopy of Glassy Dynamics

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