Glassy Disordered Systems: Glass Formation and Universal Anomalous Low-Energy Properties

✍ Scribed by Michael I. Klinger

• Publisher: World Scientific Publishing Company
• Year: 2013
• Tongue: English
• Leaves: 339
• Edition: Illustrated
• Category: Library

✦ Synopsis

The present book describes the fundamental features of glassy disordered systems at high temperatures (close to the liquid-to-glass transition) and for the first time in a book, the universal anomalous properties of glasses at low energies (i.e. temperatures/frequencies lower than the Debye values) are depicted. Several important theoretical models for both the glass formation and the universal anomalous properties of glasses are described and analyzed. The origin and main features of soft atomic-motion modes and their excitations, as well as their role in the anomalous properties, are considered in detail. It is shown particularly that the soft-mode model gives rise to a consistent description of the anomalous properties. Additional manifestations of the soft modes in glassy phenomena are described. Other models of the anomalous glassy properties can be considered as limit cases of the soft-mode model for either very low or moderately low temperatures/frequencies.

✦ Table of Contents

CONTENTS
Preface
I. Fundamental Properties of Glasses
1. General Description of Glasses and Glass Transition
1.1. Metastability and disorder. Types of glasses
1.2. Qualitative description of glass (liquid-to-glass) transition
1.3. Kinetic and thermodynamic properties
1.4. Slow relaxation processes
2. Models of Glassy (Topologically Disordered) Structures
2.1. Characteristics of glassy structures
2.2. Homogeneous (ideal) models
2.3. Inhomogeneous (cluster) models
3. Some Theoretical Models of Glass Transition
3.1. Vogel–Fulcher relation and “entropy crisis”
3.2. Role of configurational entropy, free-volume effects and “defects” diffusion
3.3. Mode-coupling model: Dynamic liquid-glass transition
4. Kohlrausch–William–Watt (KWW) Relaxation
4.1. General features of slow relaxation processes
4.2. Parallel-diffusion relaxation models
4.3. Correlated, hierarchically constrained, relaxation models
4.4. Concluding remarks
II. Anomalous Low-Energy Dynamics of Glasses
5. Origin of Anomalous Low-Energy Properties of Glasses
6. Experimental Background for Anomalous Low-Energy Atomic Dynamics
6.1. Very low temperatures and frequencies
6.2. Moderately low temperatures and frequencies
7. Soft-Mode Model of Low-Energy Atomic Dynamics
7.1. Atomic soft modes and related potentials
7.2. Probability distribution densities
7.3. Low-energy excitations: Density of states and concentration
7.4. Interaction of soft-mode excitations with acoustic phonons
8. Soft-Mode Excitations of Very Low and “Intermediate” Energies
8.1. Soft-mode tunneling states (independent two-level systems)
8.2. Soft-mode excitations of “intermediate” energies
9. Tunneling States as Very Low Energy Limit Case
9.1. Standard tunneling model: Independent two-level systems
9.2. Advanced tunneling model: Interacting two-level systems
9.2.1. Mean-field approximation: “Spectral diffusion”
9.2.2. Many-body effects: Collective excitations
10. Soft-Mode Excitations of Moderately-Low Energies (Boson Peak)
10.1. Ioffe–Regel crossover for acoustic phonons as origin of boson peak
10.2. Independent soft-mode vibrational excitations
10.3. Total vibrational density of independent soft-mode states
10.4. Generalization for interacting harmonic excitations
10.5. Total vibrational density of states: dynamic properties
10.6. Width (attenuation) of acoustic phonons
10.7. Thermal vibrational properties of glasses
11. On Universal and Non-Universal Dynamic Properties of Glasses
11.1. Very low temperatures and frequencies
11.1.1. On universality of basic distributions in ATM
11.1.2. On universality of soft-mode distribution inSMM
11.2. Moderately low temperatures and frequencies
12. Other Models for Glasses with High Frequency Sound
12.1. Theoretical mode-coupling model
12.2. Theoretical random-matrix model
12.3. Comparison with the soft-mode model
13. Recent Models for Glasses with No High-Frequency Sound
13.1. Boson peak: Ioffe–Regel crossover at elastic acoustic scattering
13.2. Dynamic and thermal anomalies at elastic acoustic scattering
13.3. Boson peak due to spatially random springs constants
13.4. Nakayama model: Boson peak vs strongly localised modes
14. Anomalous Electron Properties of Semiconducting Glasses
14.1. Basic experimental data
14.2. Negative-U centres: Anderson model
14.3. Street–Mott and Kastner–Adler–Fritzsche models
14.4. Qualitative analysis of negative-U centres
15. Soft-Mode Model of Localized Electron States in the Glasses
15.1. General considerations
15.2. Model of negative-U centres: Basic relations and approximations
15.3. Adiabatic potentials and electron energy
15.4. Basic features of self-trapped states and negative-U centres
15.5. Density of states and thermal equilibrium properties
15.6. Concluding remarks
16. Additional Manifestations of Soft Modes in Glasses
16.1. Negative-U centres model of photostructural changes in semiconducting glasses
16.2. Gap-light frequency dependence
16.3. Temperature dependence
17. Summary, Conclusions and Problems
A summary of the book can be described as follows
Several major conclusions from the SMM of low-energy excitations in glasses are also presented
Since SMM of low-energy atomic dynamics of glasses is a mean-field theory, some problems concerning the model basis and applications do not yet seem to have rigorous solutions
Acknowledgments
Appendix A. Convolution of Soft-Mode Vibrational DOS and Transformation Kernel in the DOS of BP and HFS Excitations
References
Index