Fluctuating mobility generation and transport in glasses

Wisitsorasak, Apiwat; Wolynes, Peter G.

doi:10.1103/physreve.88.022308

Cited by 30 publications

(62 citation statements)

References 28 publications

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“…However, the absolute value of the growth front velocity depends on the stability of the glass. This result was in contrast with both RFOT and pinning models, which foresee a strong temperature dependence of the growth front velocity but a small influence of the stability, 19,29 determined in our case by the deposition temperature.…”

Section: Introductioncontrasting

confidence: 53%

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The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

Ràfols‐Ribé

González-Silveira

Rodríguez-Tinoco

et al. 2017

Phys. Chem. Chem. Phys.

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Physical vapour deposition (PVD) has settled in as an alternative method to prepare glasses with significantly enhanced properties, providing new insights into the understanding of glass transition. One of the striking properties of some PVD glasses is their transformation into liquid via a heterogeneous mechanism that initiates at surfaces/interfaces. Here, we use membrane-based fast-scanning nanocalorimetry (10 4 K s À1) to analyse the variables that govern the transformation mechanism of vapourdeposited toluene glasses with different stabilities. Thin films ranging from 20 to 250 nm were prepared at deposition temperatures between 0.70 and 1.15 times the glass transition temperature. We show how a propagating growth front is the initial transformation mechanism in all the vapour deposited samples, revealing a clear tendency to faster front velocities for less stable samples. Contrary to other glassformers such as indomethacin, toluene shows a one-to-one relationship between limiting fictive temperature and front velocity. We associate this behaviour with the much simpler molecular geometry of toluene, which would prevent the presence of strong preferential molecular arrangements in the glass. However, the propagation distance of the growth front before the homogenous transformation mechanism dominates the transition is found to be dependent on the preparation conditions rather than on the thermal stability of the glass. Understanding the link between the growth variables and the properties of PVD glasses is crucial for finding and developing potential applications of this type of glass.

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Section: Introductioncontrasting

confidence: 53%

“…at surfaces and/or interfaces. 10,18 This phenomenon was already predicted by random first order transition (RFOT) theory, 19,20 facilitated kinetic Ising model calculations 21,22 and vapour deposition simulations. 23 Experimentally, this phenomenon has also been observed using a variety of techniques in several systems, e.g.…”

Section: Introductionmentioning

confidence: 95%

The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

Ràfols‐Ribé

González-Silveira

Rodríguez-Tinoco

et al. 2017

Phys. Chem. Chem. Phys.

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“…We have shown this framework quantitatively describes a broad range of experimental measurements on dynamics both in glasses and in equilibrated supercooled liquids. One of the theory's most dramatic predictions is the existence and speed of the front-like transformation of stable glasses that occurs when they are heated (10,16). The theory also predicts the hysteretic character of calorimetric experiments and the temperature dependence of the stretching exponent in the supercooled liquids and explicitly quantifies the appearance Significance When glasses are under imposed stresses or strains, they are subject to plastic deformation.…”

mentioning

confidence: 99%

“…Previously we detailed how a continuum description of the mobility-field dynamics can be derived by explicitly expanding the mode-coupling memory kernels of a spatially inhomogeneous system, using a Taylor series in terms of the gradients of the mobility that is basically the local memory kernel (10,18). To account for the random nature of molecular motion in the glasses, the equations for the mobility field are then completed by introducing stochastic terms for mobility generation and transport effects to describe a state of constrained local equilibrium.…”

mentioning

confidence: 99%

“…In this work, we show how shear bands arise dynamically by the coupling of the activated dynamics of configurationally rearranging regions with elastic strain transport. The heterogeneous activated dynamics of glasses under mechanical deformation are described using a first-principle framework based on the random first-order transition (RFOT) theory along with an extended mode-coupling theory that describes how activated events are coupled in space and time (5)(6)(7)(8)(9)(10).…”

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confidence: 99%

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Dynamical theory of shear bands in structural glasses

Wisitsorasak

Wolynes

2017

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

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The heterogeneous elastoplastic deformation of structural glasses is explored using the framework of the random first-order transition theory of the glass transition along with an extended mode-coupling theory that includes activated events. The theory involves coupling the continuum elastic theory of strain transport with mobility generation and transport as described in the theory of glass aging and rejuvenation. Fluctuations that arise from the generation and transport of mobility, fictive temperature, and stress are treated explicitly. We examine the nonlinear flow of a glass under deformation at finite strain rate. The interplay among the fluctuating fields leads to the spatially heterogeneous dislocation of the particles in the glass, i.e., the appearance of shear bands of the type observed in metallic glasses deforming under mechanical stress.glass transition | mode-coupling theory | strength of materials | shear bands W hether and how glasses flow have been fascinating questions for a long time. In the absence of stress, a glass seems to be static on human timescales, the molecules being arranged like a frozen snapshot of the liquid state. In fact, molecules in the glass are constantly moving and the glass itself is not in a state of equilibrium. Even without applied stress, molecules do change their locations through rare, activated events. These events occur at a rate that is both spatially and temporally heterogeneous. Glasses therefore continue to evolve, albeit slowly, as they approach equilibrium and age (1). These activated events are accelerated by applied stresses and typically will act to reduce the stress so that under sufficient stress the glass will not just deform elastically but visibly flow and possibly break. The deformations caused by stress are not uniform in the glass, but appear to concentrate in shear bands (2-4). In this work, we show how shear bands arise dynamically by the coupling of the activated dynamics of configurationally rearranging regions with elastic strain transport. The heterogeneous activated dynamics of glasses under mechanical deformation are described using a first-principle framework based on the random first-order transition (RFOT) theory along with an extended mode-coupling theory that describes how activated events are coupled in space and time (5-10).The random first-order transition theory of glasses is a microscopic theory that has already provided a unified quantitative description of large number of aspects of the behavior of supercooled liquids and structural glasses (11). The theory brings together two seemingly disparate aspects of glass formation: the breaking of replica symmetry that occurs in mean-field models and a theory of the activated events that tend to locally restore replica symmetry in systems with short-range interactions (7,8,(12)(13)(14). In mean-field models, there is a special temperature T d at which a dynamical transition to immobility occurs discontinuously. Above this temperature the system is well described by ordinary mode-coupli...

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Ultrastable glasses: new perspectives for an old problem

et al. 2022

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Ultrastable glasses (mostly prepared from the vapor phase under optimized deposition conditions) represent a unique class of materials with low enthalpies and high kinetic stabilities. These highly stable and dense glasses show unique physicochemical properties, such as high thermal stability, improved mechanical properties or anomalous transitions into the supercooled liquid, offering unprecedented opportunities to understand many aspects of the glassy state. Their improved properties with respect to liquid-cooled glasses also open new prospects to their use in applications where liquid-cooled glasses failed or where not considered as usable materials. In this review article we summarize the state of the art of vapor-deposited (and other) ultrastable glasses with a focus on the mechanism of equilibration, the transformation to the liquid state and the low temperature properties. The review contains information on organic, metallic, polymeric and chalcogenide glasses and an updated list with relevant properties of all materials known today to form a stable glass.

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Fluctuating mobility generation and transport in glasses

Cited by 30 publications

References 28 publications

The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

The role of thermodynamic stability in the characteristics of the devitrification front of vapour-deposited glasses of toluene

Dynamical theory of shear bands in structural glasses

Ultrastable glasses: new perspectives for an old problem

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