Glass Transition, Crystallization of Glass-Forming Melts, and Entropy

Schmelzer, Jürn W. P.; Тропин, Т. В.

doi:10.3390/e20020103

Cited by 45 publications

(83 citation statements)

References 127 publications

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“…29,34 The glass residual entropy is a non-equilibrium effect that has been extensively discussed. [37][38][39][40][41] Here, we focus on equilibrium supercooled liquids and do not discuss further the glass residual entropy and remove nonequilibrium measurements in Fig. 2.…”

Section: B Why the Configurational Entropy?mentioning

confidence: 99%

Configurational entropy of glass-forming liquids

Berthier

Ozawa

Scalliet

2019

The Journal of Chemical Physics

100

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The configurational entropy is one of the most important thermodynamic quantities characterizing supercooled liquids approaching the glass transition. Despite decades of experimental, theoretical, and computational investigation, a widely accepted definition of the configurational entropy is missing, its quantitative characterization remains fraud with difficulties, misconceptions and paradoxes, and its physical relevance is vividly debated. Motivated by recent computational progress, we offer a pedagogical perspective on the configurational entropy in glass-forming liquids. We first explain why the configurational entropy has become a key quantity to describe glassy materials, from early empirical observations to modern theoretical treatments. We explain why practical measurements necessarily require approximations that make its physical interpretation delicate. We then demonstrate that computer simulations have become an invaluable tool to obtain precise, non-ambiguous, and experimentally-relevant measurements of the configurational entropy. We describe a panel of available computational tools, offering for each method a critical discussion. This perspective should be useful to both experimentalists and theoreticians interested in glassy materials and complex systems. I. CONFIGURATIONAL ENTROPY AND GLASS FORMATION A. The glass transitionWhen a liquid is cooled, it can either form a crystal or avoid crystallization and become a supercooled liquid. In the latter case, the liquid remains structurally disordered, but its relaxation time increases so fast that there exists a temperature, called the glass temperature T g , below which structural relaxation takes such a long time that it becomes impossible to observe. The liquid is then trapped virtually forever in one of many possible structurally disordered states: this is the basic phenomenology of the glass transition. 1-4 Clearly, T g depends on the measurement timescale and shifts to lower temperatures for longer observation times. The experimental glass transition is not a genuine phase transition, as it is not defined independently of the observer.The rich phenomenology characterizing the approach to the glass transition has given rise to a thick literature. It is not our goal to review it, and we refer instead to previous articles. 1-9 There are convincing indications that the dynamic slowing down of supercooled liquids is accompanied by an increasingly collective relaxation dynamics. This is seen directly by the measurement of growing lengthscales for these dynamic heterogeneities, 10-12 or more indirectly by the growth of the apparent activation energy for structural relaxation, as seen in its non-Arrhenius temperature dependence. These observations suggest an interpretation of the experimental glass transition in terms of a generic, collective mechanism possibly controlled by a sharp phase transition. 13 'Solving the glass problem' thus amounts to identifying and obtaining direct experimental signatures about the fundamental nature and the mathematical des...

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Section: B Why the Configurational Entropy?mentioning

confidence: 99%

Configurational entropy of glass-forming liquids

Berthier

Ozawa

Scalliet

2019

The Journal of Chemical Physics

100

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“…It connects capillarity phenomena and entropy changes in the considered phase transition. Having in mind the outstanding rule of the entropy concepts in different related problems [35][36][37][38][39][40][41], such an approach can be considered already in advance as highly prospective. An extension of our method to ice-crystal nucleation in water will be presented in an accompanying paper [42].…”

Section: Introductionmentioning

confidence: 99%

Entropy and the Tolman Parameter in Nucleation Theory

Schmelzer

Abyzov

Байдаков

2019

Entropy

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Thermodynamic aspects of the theory of nucleation are commonly considered employing Gibbs’ theory of interfacial phenomena and its generalizations. Utilizing Gibbs’ theory, the bulk parameters of the critical clusters governing nucleation can be uniquely determined for any metastable state of the ambient phase. As a rule, they turn out in such treatment to be widely similar to the properties of the newly-evolving macroscopic phases. Consequently, the major tool to resolve problems concerning the accuracy of theoretical predictions of nucleation rates and related characteristics of the nucleation process consists of an approach with the introduction of the size or curvature dependence of the surface tension. In the description of crystallization, this quantity has been expressed frequently via changes of entropy (or enthalpy) in crystallization, i.e., via the latent heat of melting or crystallization. Such a correlation between the capillarity phenomena and entropy changes was originally advanced by Stefan considering condensation and evaporation. It is known in the application to crystal nucleation as the Skapski–Turnbull relation. This relation, by mentioned reasons more correctly denoted as the Stefan–Skapski–Turnbull rule, was expanded by some of us quite recently to the description of the surface tension not only for phase equilibrium at planar interfaces, but to the description of the surface tension of critical clusters and its size or curvature dependence. This dependence is frequently expressed by a relation derived by Tolman. As shown by us, the Tolman equation can be employed for the description of the surface tension not only for condensation and boiling in one-component systems caused by variations of pressure (analyzed by Gibbs and Tolman), but generally also for phase formation caused by variations of temperature. Beyond this particular application, it can be utilized for multi-component systems provided the composition of the ambient phase is kept constant and variations of either pressure or temperature do not result in variations of the composition of the critical clusters. The latter requirement is one of the basic assumptions of classical nucleation theory. For this reason, it is only natural to use it also for the specification of the size dependence of the surface tension. Our method, relying on the Stefan–Skapski–Turnbull rule, allows one to determine the dependence of the surface tension on pressure and temperature or, alternatively, the Tolman parameter in his equation. In the present paper, we expand this approach and compare it with alternative methods of the description of the size-dependence of the surface tension and, as far as it is possible to use the Tolman equation, of the specification of the Tolman parameter. Applying these ideas to condensation and boiling, we derive a relation for the curvature dependence of the surface tension covering the whole range of metastable initial states from the binodal curve to the spinodal curve.

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“…When the temperature is above T g , an amorphous solid exists in a "rubbery" state. In this state, the molecular mobility of the matrix and the reactants are accelerated, which results in an increased rate of Physico-chemical changes in dried products, such as sticking, caking, collapse, crystallization, agglomeration, loss of volatiles, browning, and oxidation [47][48][49]. In freeze-drying, collapse is a frequent problem if certain operation variables are not well set [50].…”

Section: Glass Transition During Freeze-dryingmentioning

confidence: 99%

Effect of Freeze-Drying on Quality and Grinding Process of Food Produce: A Review

2020

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Freeze-drying is an important processing unit operation in food powder production. It offers dehydrated products with extended shelf life and high quality. Unfortunately, food quality attributes and grinding characteristics are affected significantly during the drying process due to the glass transition temperature (during drying operation) and stress generated (during grinding operation) in the food structure. However, it has been successfully applied to several biological materials ranging from animal products to plants products owning to its specific advantages. Recently, the market demands for freeze-dried and ground food products such as spices, vegetables, and fruits are on the increase. In this study, the effect of the freeze-drying process on quality attributes, such as structural changes, the influence of glass transition during grinding, together with the effect on grinding efficiency in terms of energy requirement, grinding yield, and morphological changes in the powder as a result of temperature, drying time were discussed. An overview of models for drying kinetics for freeze-dried food sample, and grinding characteristics developed to optimize the drying processes, and a prediction of the grinding characteristics are also provided. Some limitations of the drying process during grinding are also discussed together with innovative methods to improve the drying and grinding processes.

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Glass Transition, Crystallization of Glass-Forming Melts, and Entropy

Cited by 45 publications

References 127 publications

Configurational entropy of glass-forming liquids

Configurational entropy of glass-forming liquids

Entropy and the Tolman Parameter in Nucleation Theory

Effect of Freeze-Drying on Quality and Grinding Process of Food Produce: A Review

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