scholarly journals Ergodicity and slowing down in glass-forming systems with soft potentials: No finite-temperature singularities

2008 ◽  
Vol 78 (1) ◽  
Author(s):  
Jean-Pierre Eckmann ◽  
Itamar Procaccia
Keyword(s):  
Finite Temperature ◽  
Glass Forming ◽  
Slowing Down

scholarly journals Fast Vibrational Modes and Slow Heterogeneous Dynamics in Polymers and Viscous Liquids

2019 ◽  
Vol 20 (22) ◽  
pp. 5708 ◽  
Author(s):  
Francesco Puosi ◽  
Antonio Tripodo ◽  
Dino Leporini
Keyword(s):  
Einstein Relation ◽  
Special Focus ◽  
Vibrational Dynamics ◽  
Viscous Liquids ◽  
Dynamical Heterogeneity ◽  
Glass Forming ◽  
Slowing Down ◽  
Molecular Glass ◽  
Distinctive Aspect ◽  
Glass Forming Materials

Many systems, including polymers and molecular liquids, when adequately cooled and/or compressed, solidify into a disordered solid, i.e., a glass. The transition is not abrupt, featuring progressive decrease of the microscopic mobility and huge slowing down of the relaxation. A distinctive aspect of glass-forming materials is the microscopic dynamical heterogeneity (DH), i.e., the presence of regions with almost immobile particles coexisting with others where highly mobile ones are located. Following the first compelling evidence of a strong correlation between vibrational dynamics and ultraslow relaxation, we posed the question if the vibrational dynamics encodes predictive information on DH. Here, we review our results, drawn from molecular-dynamics numerical simulation of polymeric and molecular glass-formers, with a special focus on both the breakdown of the Stokes–Einstein relation between diffusion and viscosity, and the size of the regions with correlated displacements.

LOOKING AT THE GLASS TRANSITION: CHALLENGES OF EXTREME TIME SCALES AND OTHER INTERESTING PROBLEMS

2020 ◽  
Vol 93 (1) ◽  
pp. 79-120 ◽  
Author(s):  
Gregory B. McKenna
Keyword(s):  
Glass Transition ◽  
Time Scales ◽  
Finite Temperature ◽  
Glassy State ◽  
Metastable Equilibrium ◽  
Arrhenius Behavior ◽  
Fictive Temperature ◽  
Major Question ◽  
Kauzmann Temperature ◽  
Glass Forming

ABSTRACT The behavior of glass-forming materials is examined with emphasis on the below-glass transition behavior. A major question that is related to the super-Arrhenius behavior of the dynamics of glass-forming systems is whether the apparent divergence at finite temperature continues below the kinetic or laboratory glass transition that is related to the limits of measurement and is standardized so that the material relaxation time is near 100 s. The problem arises because as the temperature decreases, the time scales required to reach equilibrium (or metastable equilibrium) become geologically long. Yet the apparent finite temperature divergence is fundamental to many theories of glasses; therefore, it becomes essential to find ways to finesse the extreme time scales related to the so-called Kauzmann paradox to bring new information to the ongoing conversation concerning the existence or not of an ideal glass transition at either the Kauzmann temperature or the Vogel–Fulcher–Tammann temperature. After describing the framework of the glassy state that is formed by the early ideas of a fictive temperature, we examine the use of extremely low fictive temperature glasses as a means to potentially get around the long time-scale problem. The challenge is to find ways to create such glasses and measure their properties. In addition to looking at the dynamic behavior of a 20-million-year-old amber and a vapor-deposited amorphous perfluoropolymer whose fictive temperature was the same as the Kauzmann temperature for the material, we also examine the possibility of directly testing the thermodynamics of an ideal glass transition by making athermal solutions of a poly(α-methyl styrene) and its pentamer, where we find that the entropy surface determined from extrapolation of the heat capacity to zero pentamer shows no distinct transition at as much as 180 K below the Kauzmann temperature. The significance of the dynamics of the stable glasses and the thermodynamics of the polymer solutions is discussed in terms that challenge the idea of an ideal glass transition. We also look in more detail at the ability to use vapor deposition to make ethylbenzene, a small-molecule organic, into an ultra-stable glass with a fictive temperature that is possibly below the Kauzmann temperature of this material. We end with remarks on the question of decoupling of different relaxation mechanisms as something not treated by current theories of glass, and we consider some open questions related to the fact that the glass transition remains an unresolved and important problem.

scholarly journals Qubit Dynamics in a q-Deformed Oscillators Environment

2010 ◽  
Vol 17 (01) ◽  
pp. 73-87 ◽  
Author(s):  
Sonia L'Innocente ◽  
Cosmo Lupo ◽  
Stefano Mancini
Keyword(s):  
Finite Temperature ◽  
Quantum Coherence ◽  
Slowing Down ◽  
Fermionic Case

We study the dynamics of one and two qubits plunged in a q-deformed oscillators environment. Specifically we evaluate the decay of quantum coherence and entanglement in time when passing from bosonic to fermionic environments. Slowing down of decoherence in the fermionic case is found. The effect manifests itself only at finite temperature.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

The effect of an aluminum heat-sink layer on the laser-induced amorphization of SiOx/TeGeSn/SiOx phase-change recording films

1989 ◽  
Vol 47 ◽  
pp. 574-575
Author(s):  
Matthew R. Libera ◽  
Martin Chen
Keyword(s):  
Thin Film ◽  
Phase Change ◽  
Heat Sink ◽  
Multilayer Film ◽  
Glassy Phase ◽  
Film Structure ◽  
Glass Forming ◽  
Active Storage ◽  
Dielectric Layers ◽  
Amorphous States

Phase-change erasable optical storage is based on the ability to switch a micron-sized region of a thin film between the crystalline and amorphous states using a diffraction-limited laser as a heat source. A bit of information can be represented as an amorphous spot on a crystalline background, and the two states can be optically identified by their different reflectivities. In a typical multilayer thin-film structure the active (storage) layer is sandwiched between one or more dielectric layers. The dielectric layers provide physical containment and act as a heat sink. A viable phase-change medium must be able to quench to the glassy phase after melting, and this requires proper tailoring of the thermal properties of the multilayer film. The present research studies one particular multilayer structure and shows the effect of an additional aluminum layer on the glass-forming ability.

Crystallization in Al 88 RE 8 Ni 4 glass-forming alloys

2002 ◽  
Vol 82 (12) ◽  
pp. 2483-2497 ◽  
Author(s):  
T. K. Croat ◽  
A. K. Gangopadhyay ◽  
K. F. K Elton
Keyword(s):  
Glass Forming

Study of the ?-Mechanical Relaxation in Molecular Glass-Forming Liquids

1997 ◽  
Vol 7 (11) ◽  
pp. 1635-1650 ◽  
Author(s):  
A. Faivre ◽  
L. David ◽  
J. Perez
Keyword(s):  
Mechanical Relaxation ◽  
Glass Forming ◽  
Molecular Glass
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