Non-exponential structural relaxation, anomalous light scattering and nanoscale inhomogeneities in glass-forming liquids

Moynihan, Cornelius T.; Schroeder, John

doi:10.1016/0022-3093(93)90283-4

Cited by 195 publications

(145 citation statements)

References 30 publications

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“…30)). This increase could be attributed to a different relaxation mechanism in the glassy state or to a narrowing of the distribution of relaxations, which gives rise to the well-known stretched exponential behaviour observed in supercooled liquids 1,2,38 . Similar behaviour of the density fluctuations has been also reported in molecular dynamic simulations 39,40 and dielectric spectroscopy studies of polymeric glasses 41 .…”

Section: Resultsmentioning

confidence: 96%

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Revealing the fast atomic motion of network glasses

Baldi²,

et al. 2014

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Still very little is known on the relaxation dynamics of glasses at the microscopic level due to the lack of experiments and theories. It is commonly believed that glasses are in a dynamical arrested state, with relaxation times too large to be observed on human time scales. Here we provide the experimental evidence that glasses display fast atomic rearrangements within a few minutes, even in the deep glassy state. Following the evolution of the structural relaxation in a sodium silicate glass, we find that this fast dynamics is accompanied by the absence of any detectable aging, suggesting a decoupling of the relaxation time and the viscosity in the glass. The relaxation time is strongly affected by the network structure with a marked increase at the mesoscopic scale associated with the ion-conducting pathways. Our results modify the conception of the glassy state and asks for a new microscopic theory.

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Section: Resultsmentioning

confidence: 96%

“…Following the Tool-Narayanaswamy-Moynihan model (TNM) 38,[49][50][51] , we can use the thermal protocol followed during the experiments to estimate the evolution of the fictive temperature 45 and of the relaxation time that one would expect from macroscopic measurements, through the relations:…”

Section: Resultsmentioning

confidence: 99%

Revealing the fast atomic motion of network glasses

Baldi²,

et al. 2014

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“…Such a high value is in agreement with the results reported for other metallic glasses, 23,24 while it cannot be explained within the current theories for the dynamics in the glassy state. [36][37][38] Based on the J. Chem. Phys.…”

Section: Resultsmentioning

confidence: 99%

“…27,31 This behavior seems to be universal in metallic glasses 23,24 and cannot be explained by the well-known theories for glasses dynamics, which predict a stretched exponential shape of the correlation functions, even in the glassy state. [36][37][38] Model systems such as hard spheres and Lennard-Jones are unable to reproduce these intriguing dynamic effects. 18,20 In these model systems, indeed, the dynamics appears to be always characterized by a broad spectrum of relaxations.…”

Section: Discussionmentioning

confidence: 99%

Compressed correlation functions and fast aging dynamics in metallic glasses

Ruta

Baldi²,

Monaco

et al. 2013

The Journal of Chemical Physics

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We present x-ray photon correlation spectroscopy measurements of the atomic dynamics in a Zr 67 Ni 33 metallic glass, well below its glass transition temperature. We find that the decay of the density fluctuations can be well described by compressed, thus faster than exponential, correlation functions which can be modeled by the well-known Kohlrausch-Williams-Watts function with a shape exponent β larger than one. This parameter is furthermore found to be independent of both waiting time and wave-vector, leading to the possibility to rescale all the correlation functions to a single master curve. The dynamics in the glassy state is additionally characterized by different aging regimes which persist in the deep glassy state. These features seem to be universal in metallic glasses and suggest a nondiffusive nature of the dynamics. This universality is supported by the possibility of describing the fast increase of the structural relaxation time with waiting time using a unique model function, independently of the microscopic details of the system.

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“…On the other hand, the 2 nm dimension has been attributed to fluctuations in the dielectric constant of glassformers near their T g , based on an excess light scattering observed on cycling through the glass transformation zone 27 . This would imply that density variations of this magnitude are being detected.…”

Section: Introductionmentioning

confidence: 99%

On the Decoupling of Relaxation Modes in a Molecular Liquid Caused by Isothermal Introduction of 2 nm Structural Inhomogeneities

Ueno

Angell²

2011

J. Phys. Chem. B

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To support a new interpretation of the origin of the dynamic heterogeneity observed pervasively in fragile liquids as they approach their glass transition temperatures T g , we demonstrate that the introduction of ~2 nm structural inhomogeneities into a homogeneous glassformer leads to a decoupling of diffusion from viscosity similar to that observed during the cooling of orthoterphenyl OTP below T A, where Arrhenius behavior is lost. Further, the decoupling effect grows stronger as temperature decreases (and viscosity increases). The liquid is cresol and the ~2nm inhomogeneities are cresol-soluble asymmetric derivatized tetrasiloxy-based (POSS) molecules. The decoupling is the phenomenon predicted by Onsager in discussing the approach to a liquid-liquid phase separation with decreasing temperature. In the present case the observations support the notion of a polyamorphic transition in fragile liquids that is hidden below the glass transition. A similar decoupling can be expected as a globular protein is dissolved in dilute aqueous solutions or in protic ionic liquids. IntroductionOne of the most intensively researched aspects of glassforming liquids is the heterogeneity that develops in their dynamic properties as temperature is decreased from above the melting point to deep in the supercooled liquid state 1-6 7,8 . It is found that, except for the case of polymer liquids, the behavior at high temperatures is simple: fluctuations, such as those explored by neutron scattering through the self-intermediate scattering function, relax exponentially on time scales that follow the simple Arrhenius equation. Then at temperatures that are usually, but not necessarily, below the melting point, (i) a shoulder develops in the relaxation function, (ii) the longer time component of the relaxation function becomes non-exponential and (iii) the temperature dependence of the relaxation time (both average and most probable) departs from Arrhenius behavior

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Non-exponential structural relaxation, anomalous light scattering and nanoscale inhomogeneities in glass-forming liquids

Cited by 195 publications

References 30 publications

Revealing the fast atomic motion of network glasses

Revealing the fast atomic motion of network glasses

Compressed correlation functions and fast aging dynamics in metallic glasses

On the Decoupling of Relaxation Modes in a Molecular Liquid Caused by Isothermal Introduction of 2 nm Structural Inhomogeneities

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