Connection between slow and fast dynamics of molecular liquids around the glass transition

Niss, Kristine; Dalle-Ferrier, Cécile; Frick, B.; Russo, Daniela; Dyre, Jeppe C.; Alba‐Simionesco, Christiane

doi:10.1103/physreve.82.021508

Cited by 33 publications

(40 citation statements)

References 77 publications

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“…In some liquids fast relaxation occurs at the nanosecond time scale [29], which will presumably contribute to the total entropy as well. This putative "fast relaxational" entropy term is not incorporated in this analysis.…”

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confidence: 99%

Correlations between Vibrational Entropy and Dynamics in Liquids

Wyart

2010

Phys. Rev. Lett.

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A relation between vibrational entropy and particles mean square displacement is derived in supercooled liquids, assuming that the main effect of temperature changes is to rescale the vibrational spectrum. Deviations from this relation, in particular due to the presence of a Boson peak whose shape and frequency changes with temperature, are estimated. Using observations of the short-time dynamics in liquids of various fragility, it is argued that (i) if the crystal entropy is significantly smaller than the liquid entropy at Tg, the extrapolation of the vibrational entropy leads to the correlation TK ≈ T0, where TK is the Kauzmann temperature and T0 is the temperature extracted from the Vogel-Fulcher fit of the viscosity. (ii) The jump in specific heat associated with vibrational entropy is very small for strong liquids, and increases with fragility. The analysis suggests that these correlations stem from the stiffening of the Boson peak under cooling, underlying the importance of this phenomenon on the dynamical arrest.PACS numbers: 64.70. Pf, When a liquid is cooled sufficiently rapidly to avoid crystallization, the relaxation time τ below which it behaves as a solid increases up to the glass transition temperature T g where the liquid falls out of equilibrium. In strong liquids τ displays an Arrhenius dependence on temperature, but in other liquids, said to be fragile, the slowing-down of the dynamics is much more pronounced. In general the dynamics is well captured by the VogelFulcher law log(τ ) = C + U/(T − T 0 ), although nondiverging functional forms can also reproduce the dynamics well [1]. As the temperature evolves, two quantities appear to be good predictors of τ : the space available for the rattling of the particles on the picosecond time scales [2,3], embodied by the particles mean square displacement u 2 observable in scattering experiments, and the difference between the liquid and the crystal entropy [4]. When extrapolated below T g this quantity vanishes at some T K , the Kauzmann temperature [5], which appears to correspond rather well to the temperature T 0 extracted from the Vogel-Fulcher law [6]. The correlation between dynamics and thermodynamics has been interpreted early on as the signature of a thermodynamical transition at T K toward an ideal glass where the configurational entropy associated with the number of metastable states visited by the dynamics, or inherent structures, would vanish [7]. This view is appealing and still influential today [8,9], although it is not devoid of conceptual problems [10]. Elastic models [11][12][13] propose an alternative scenario of the glass transition: fragile liquids are simply those which stiffen under cooling, reducing the particle mean square displacement and increasing the activation barriers that must be overcome to flow. In this view the rapid change of entropy in fragile liquids stem from the temperature dependence of the high-frequency elastic moduli [14]. This is consistent with some observations supporting that fragile liquids stiffen mor...

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confidence: 99%

Correlations between Vibrational Entropy and Dynamics in Liquids

Wyart

2010

Phys. Rev. Lett.

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“…The system size effects on these states will be discussed elsewhere. Experimental studies show a sudden change of slope in the temperature dependence of MSD at glass transition temperatures T g [7,8]. Extensive studies of non-diffusive states of systems of WCA spheres, revealed that temperature dependence of MSD shows a transition similar to those observed in experiments.…”

Section: Hopping Dynamics In Monodispersed Isotropic Spheresmentioning

confidence: 56%

Molecular Dynamics Simulations of One-, Two-, Three-dimensional Hopping Dynamics

Aoki¹,

Fujiwara²,

Sogo³

et al. 2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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“…Cumene has been studied for many years with other techniques, for example in Refs. 32,[43][44][45][46] . Cumene is a fragile liquid (m ≈ 70) with only a very small beta relaxation.…”

Section: The Experiments and Datamentioning

confidence: 99%

“…Since the thermal motion that gives rise to the transition is dominated by phonons, it is argued that the relevant time scale should be the picosecond time scale. However, for some liquids elastic models appear to work better when tested at longer time scales where the properties are more temperature dependent than at the phonon-times 32,33 . In other words, the temperature dependence of the vibration on the phonon time scale is not always large enough to account for the super-Arrhenius temperature dependence of the relaxation time.…”

Section: Introductionmentioning

confidence: 99%

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Connection between fragility, mean-squared displacement, and shear modulus in two van der Waals bonded glass-forming liquids

Hansen¹,

Frick²,

Hecksher³

et al. 2017

Phys. Rev. B

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The temperature dependence of the high-frequency shear modulus measured in the kHz range is compared to the mean-squared displacement measured in the nanosecond range for the two van der Waals bonded glass-forming liquids cumene and 5PPE. This provides an experimental test for the assumption connecting two versions of the shoving model for the non-Arrhenius temperature dependence of the relaxation time in glass formers. The two versions of the model are also tested directly and both are shown to work well for these liquids.

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Connection between slow and fast dynamics of molecular liquids around the glass transition

Cited by 33 publications

References 77 publications

Correlations between Vibrational Entropy and Dynamics in Liquids

Correlations between Vibrational Entropy and Dynamics in Liquids

Molecular Dynamics Simulations of One-, Two-, Three-dimensional Hopping Dynamics

Connection between fragility, mean-squared displacement, and shear modulus in two van der Waals bonded glass-forming liquids

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