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Author: Jacob D. Stevenson
Publisher:
ISBN: 9781109135824
Category :
Languages : en
Pages : 91
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Book Description
Why glasses behave like solids in the absence of their having any long range structural order, is a fundamental problem of statistical physics, one that has been actively researched for more than 80 years. Supported by the mean field theory of supercooled liquids and a deep connection to mean field spin glasses with one step replica symmetry breaking, the random first order transition theory offers a solution to the glass problem based on assuming proximity to an underlying ideal glass transition. In the deeply supercooled liquid the free energy landscape is dominated by metastable structural basins separated by large free energy barriers. The rate of inter-conversion between these structural states is ultimately driven by the entropic cost of remaining confined to one basin, a cost which is quantified by the configurational entropy. Both the activation free energy barrier and the number of cooperatively moving particles required to overcome the barrier diverge as the ideal glass transition is approached. The cooperative nature of the dynamics in the deeply supercooled liquid regime has been confirmed by experiments and simulations and has been the subject of intense study in recent years. In the following we explore the implications of cooperative dynamics in the random first order transition theory with particular focus on the expected behavior at the ideal glass transition temperature and at the dynamical crossover, the temperature where activated motions first become important. We also show how the general features of secondary relaxation can be recovered by adding local fluctuations to the equations describing cooperative reconfiguration. Finally, we describe how cooperatively rearranging regions modify dynamics near the surface of glasses, reducing the apparent viscosity by several orders of magnitude.
Author: Jacob D. Stevenson
Publisher:
ISBN: 9781109135824
Category :
Languages : en
Pages : 91
Get Book Here
Book Description
Why glasses behave like solids in the absence of their having any long range structural order, is a fundamental problem of statistical physics, one that has been actively researched for more than 80 years. Supported by the mean field theory of supercooled liquids and a deep connection to mean field spin glasses with one step replica symmetry breaking, the random first order transition theory offers a solution to the glass problem based on assuming proximity to an underlying ideal glass transition. In the deeply supercooled liquid the free energy landscape is dominated by metastable structural basins separated by large free energy barriers. The rate of inter-conversion between these structural states is ultimately driven by the entropic cost of remaining confined to one basin, a cost which is quantified by the configurational entropy. Both the activation free energy barrier and the number of cooperatively moving particles required to overcome the barrier diverge as the ideal glass transition is approached. The cooperative nature of the dynamics in the deeply supercooled liquid regime has been confirmed by experiments and simulations and has been the subject of intense study in recent years. In the following we explore the implications of cooperative dynamics in the random first order transition theory with particular focus on the expected behavior at the ideal glass transition temperature and at the dynamical crossover, the temperature where activated motions first become important. We also show how the general features of secondary relaxation can be recovered by adding local fluctuations to the equations describing cooperative reconfiguration. Finally, we describe how cooperatively rearranging regions modify dynamics near the surface of glasses, reducing the apparent viscosity by several orders of magnitude.
Author: Peter G. Wolynes
Publisher: John Wiley & Sons
ISBN: 0470452234
Category : Science
Languages : en
Pages : 422
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Book Description
With contributions from 24 global experts in diverse fields, and edited by world-recognized leaders in physical chemistry, chemical physics and biophysics, Structural Glasses and Supercooled Liquids: Theory, Experiment, and Applications presents a modern, complete survey of glassy phenomena in many systems based on firmly established characteristics of the underlying molecular motions as deduced by first principle theoretical calculations, or with direct/single-molecule experimental techniques. A well-rounded view of a variety of disordered systems where cooperative phenomena, which are epitomized by supercooled liquids, take place is provided. These systems include structural glasses and supercooled liquids, polymers, complex liquids, protein conformational dynamics, and strongly interacting electron systems with quenched/self-generated disorder. Detailed calculations and reasoned arguments closely corresponding with experimental data are included, making the book accessible to an educated non-expert reader.
Author: Liang Hong
Publisher:
ISBN:
Category : Glass transition temperature
Languages : en
Pages : 199
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Book Description
"Although glass has been fabricated for thousands of years, the microscopic mechanism governing the glass transition process remains unclear. The main challenge is to understand the non-Arrhenius temperature dependence of the structural relaxation time of the supercooled liquids upon approaching the glass transition temperature. Most researchers ascribe it to cooperative molecular motions. Various experimental results and simulations show that the structural relaxation of a supercooled liquid is spatially heterogeneous. This dynamic heterogeneity is usually attributed to the cooperative molecular motions in local domains. The cooperativity size is estimated from the spatial heterogeneity to be ~1-4 nanometers. However, many important questions are still unsolved, e.g. what is the role of molecular cooperativity in the temperature dependence of the structural relaxation time? On the other hand, the collective vibration in the GHz-THz frequency range, the so-called boson peak, is also considered to be a manifestation of a cooperative process with a characteristic length scale of a few nanometers. Some researchers even speculate that the length scale associated with the boson peak is related to the cooperativity length scale of the main structural relaxation. In this dissertation, we estimated the characteristic length scale from the boson peak spectra measured using light scattering for a large number of glass-forming materials. By comparing it to the dynamic heterogeneity length scale of the main structural relaxation acquired via 4-dimensional NMR, we find that the collective vibrations and the structural relaxation involve a similar length scale of molecular cooperativity. When a supercooled liquid is cooled down to the glass transition temperature, decreases in free volume and thermal energy both contribute to slowing down the structural relaxation. Our analysis demonstrates that only the volume contribution to the variation of the structural relaxation time has a direct correlation with the cooperativity size among different materials, whereas the thermal energy contribution does not. The latter is more dependent on the chemical structure of the studied materials. These results call for a conceptually new approach to the analysis of the mechanism of the glass transition and to the role of molecular cooperativity."--Abstract.
Author: Mauro Merolle
Publisher:
ISBN:
Category :
Languages : en
Pages : 264
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Book Description
Author: Connie B. Roth
Publisher: CRC Press
ISBN: 1315305143
Category : Science
Languages : en
Pages : 573
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Book Description
"the present book will be of great value for both newcomers to the field and mature active researchers by serving as a coherent and timely introduction to some of the modern approaches, ideas, results, emerging understanding, and many open questions in this fascinating field of polymer glasses, supercooled liquids, and thin films" –Kenneth S. Schweizer, Morris Professor of Materials Science & Engineering, University of Illinois at Urbana-Champaign (from the Foreword) This book provides a timely and comprehensive overview of molecular level insights into polymer glasses in confined geometries and under deformation. Polymer glasses have become ubiquitous to our daily life, from the polycarbonate eyeglass lenses on the end of our nose to large acrylic glass panes holding water in aquarium tanks, with advantages over glass in that they are lightweight and easy to manufacture, while remaining transparent and rigid. The contents include an introduction to the field, as well as state of the art investigations. Chapters delve into studies of commonalities across different types of glass formers (polymers, small molecules, colloids, and granular materials), which have enabled microscopic and molecular level frameworks to be developed. The authors show how glass formers are modeled across different systems, thereby leading to treatments for polymer glasses with first-principle based approaches and molecular level detail. Readers across disciplines will benefit from this topical overview summarizing the key areas of polymer glasses, alongside an introduction to the main principles and approaches.
Author: Michael Miller
Publisher: Springer Science & Business Media
ISBN: 0387489215
Category : Technology & Engineering
Languages : en
Pages : 243
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Book Description
Bulk metallic glasses are a new emerging field of materials with many desirable and unique properties. These amorphous materials have many diverse applications from structural applications to biomedical implants. This book provides a complete overview of bulk metallic glasses. It covers the principles of alloy design, glass formation, processing, atomistic modeling, computer simulations, mechanical properties and microstructures.
Author: Tosi Mario P
Publisher: World Scientific
ISBN: 9814547417
Category :
Languages : en
Pages : 408
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Book Description
This volume contains the Proceedings of the International Workshop on “Non-Equilibrium Phenomena in Supercooled Fluids, Glasses and Amorphous Materials”, held in Pisa in the early fall of 1995 as a joint initiative of the University of Pisa and of the Scuola Normale Superiore. The goal was to bring together liquid state physicists, chemists and engineers, to review current developments and comparatively discuss experimental facts and theoretical predictions in this vast scientific area. The core of the Workshop was a set of general lectures followed by more specific presentations on current issues in the main areas of the field. This structure has been maintained in this volume, in which a set of five overviews is followed by topically grouped contributions in the five areas of ionic glasses and glassy materials, the glass transition, viscous flow and microscopic relaxation, complex fluids, and polymers. The volume also preserves a record of the many short contributions given to the Workshop through posters, which are grouped in it under the subjects of inorganic glasses, organic glasses and complex fluids, polymers, and theoretical aspects.
Author: Behrooz Movahedi
Publisher: BoD – Books on Demand
ISBN: 9535125117
Category : Technology & Engineering
Languages : en
Pages : 180
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Book Description
Metallic glasses and amorphous materials have attracted much more attention in the last two decades. A noncrystalline solid produced by continuous cooling from the liquid state is known as a glass. From the other point of view, a noncrystalline material, obtained by any other process, for example, vapor deposition or solid-state processing methods such as mechanical alloying, but not directly from the liquid state, is referred to as an amorphous material. At this moment, bulk metallic glasses (BMG) are appearing as a new class of metallic materials with unique physical and mechanical properties for structural and functional usage. Extreme values of strength, fracture toughness, magnetic properties, corrosion resistance, and other properties have been registered in BMG materials.
Author: Sylwester J. Rzoska
Publisher: Springer Science & Business Media
ISBN: 1402027044
Category : Science
Languages : en
Pages : 395
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Book Description
Complex liquids constitute a basic element in modern materials science; their significant features include self-assembly, mesoscale structures, complex dynamics, unusual phases and enormous sensitivity to perturbations. Understanding their nature and properties are a great challenge to modern materials science that demands novel approaches. This book focuses on nonlinear dielectric phenomena, particularly on nonlinear dielectric spectroscopy (NDS), which may be considered a possible successor to broadband dielectric spectroscopy (BDS). NDS phenomena directly coupled to mesoscale heterogeneity fluctuations, so information obtained in this way is basically complementary to BDS tests. The book also discusses the application of NDS in a set of complex liquid systems: glassy liquids, liquid crystals, liquids with critical point phenomena, and bio-relevant liquids. The complementary application of NDS and BDS may allow the discovery of universal patterns for the whole category of complex liquids. Written by specialists in the field of nonlinear dielectric studies, theoreticians and experimentalists, ranging from solid state physics to biophysics, the book is organized so that it can serve as a basic textbook for a non-experienced reader.
Author: Antonio Coniglio
Publisher: Elsevier
ISBN: 0080474683
Category : Science
Languages : en
Pages : 232
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Book Description
Deep connections are emerging in the physics of non-thermal systems,such as granular media, and other "complex systems" such as glass formers, spin glasses, colloids or gels. This book discusses the unifying physical theories, developed in recent years, for the description of these systems. The special focus of the book is on recent important developments in the formulation of a Statistical Mechanics approach to granular media and the description of out-of-equilibrium dynamics, such as "jamming" phenomena, ubiquitous in these "complex systems". The book collects contributions from leading researchers in these fields, providing both an introduction, at a graduate level, to these rapidly developing subjects and featuring an up to date, self contained, presentation of theoretical and experimental developments for researchers in areas ranging from Chemistry, to Engineering and Physical Sciences.·the book discusses very hot topics in physical sciences·it includes contributions from the most prominent researchers in the area·it is clearly written and self contained
