Disordered Solids, 1989 Structures and Processes Physical Sciences Series

This book presents an account of the course "Disordered Solids: Structures and Processes" held in Erice, Italy, from June 15 to 29, 1987. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The objective of this course was to present the advances in physical modelling, mathematical formalism and experimental techniques relevant to the interpretation of the structures of disordered solids and of the physical processes occurring therein. Traditional solid-state physics treats solids as perfect crystals and takes great advantage of their symmetry, by means of such mathematical formalisms as the reciprocal lattice, the Brillouin zone, and the powerful tools of group theory. Even if in reality no solid is a perfect crystal, this theoretical approach has been of great usefulness in describing solids: deviations from perfect order have been treated as perturbations of the ideal model. A new situation arises with truly disordered solids where any vestige of long range order has disappeared. The basic problem is that of describing these systems and gaining a scientific understanding of their physical properties without the mathematical formalism of traditional solid­ state physics. While some of the old approaches may occasionally remain valid (e. g. chemical bonding approach for amorphous solids), the old ways will not do. Disorder is not a perturbation: with disorder, something basically new may be expected to appear.

The Evolving Notion of Order.- Probabilistic Methods in Physics.- Dynamical Processes in Disordered Systems.- Sharp Spectral Lines of Luminescent Centers in Solids.- Localization and Percolation in Alloy Semiconductors.- Electronic Properties of Amorphous Semiconductors: An Introduction.- Excitations and Phase Transitions of Disordered Magnetic Systems.- Spin Glasses.- Optical Techniques and Experimental Investigation of Diffusion Processes in Disordered Media.- Long Seminars, Detection of Protonic Percolation on Hydrated Lysozyme Powders.- Fluctuations in Systems Subject to External Forces.- Spectroscopy of Inorganic Glasses.- Effects of Disorder on the Spectral Properties of Cr-Doped Glasses, Glassceramics and Crystals.- Physics and Spectroscopy of Laser Insulating Crystals with Disordered Structure.- Fractal Behavior of Porous Glasses.- Photochemical Hole Burning (Abstract Only).- Short Seminars (Titles Only).- Special Topic, Fundamental Interactions of Elementary Particles: Discoveries and Perspectives.- Summary of the Meeting.- Participants.