Structure And Bonding In Noncrystalline Solids

Noncrystalline (NC) solids, as is well known, lack the long range order of crystals. Accordingly, they exhibit scattering, e.g., x-ray, electron, and neutron, but not the diffraction patterns characteristic of crystals. The intensity distributions from NC solids are usually transformed into radial distribution functions (RDF), but the interpretation of the RDF's is not unique. The lack of long-range order, and the non-uniqueness of the structural interpretation, have constituted the main obstacles to the usual solid state physics approach which has been so successful in dealing with crystals. As a corrolary, questions of local order and structure have frequently been de-emphasized. This monograph contains a collection of chapters many of which emphasize local-structure and chemical bonding as opposed to long-range order. Most of the chapters were chosen from talks given at the international symposium, "Structure and Bonding in Noncrystalline Solids," held in Reston, Virginia in May of 1983. Other chapters, however, were simply submitted independently of the Reston conference. Thus, this book is not a proceedings of that conference, nor was it ever intended to be. The chapters presented here range from theory of bonding and structure, to structurally oriented measurements of various kinds, e.g., ESR, Raman, to more applied chapters. Our goal was to produce a monograph that enhances understanding of the structures of NC solids.

Noncrystalline (NC) solids, as is well known, lack the long range order of crystals. Accordingly, they exhibit scattering, e.g., x-ray, electron, and neutron, but not the diffraction patterns characteristic of crystals. The intensity distributions from NC solids are usually transformed into radial distribution functions (RDF), but the interpretation of the RDF's is not unique. The lack of long-range order, and the non-uniqueness of the structural interpretation, have constituted the main obstacles to the usual solid state physics approach which has been so successful in dealing with crystals. As a corrolary, questions of local order and structure have frequently been de-emphasized. This monograph contains a collection of chapters many of which emphasize local-structure and chemical bonding as opposed to long-range order. Most of the chapters were chosen from talks given at the international symposium, "Structure and Bonding in Noncrystalline Solids," held in Reston, Virginia in May of 1983. Other chapters, however, were simply submitted independently of the Reston conference. Thus, this book is not a proceedings of that conference, nor was it ever intended to be. The chapters presented here range from theory of bonding and structure, to structurally oriented measurements of various kinds, e.g., ESR, Raman, to more applied chapters. Our goal was to produce a monograph that enhances understanding of the structures of NC solids.

Structure and Bonding in Crystals presents a new understanding of the older topics such as bond length, bond strength, and ionic radii. These concepts have been used by geochemists and geophysicists to systematize and predict phase transitions at high pressure. The final group of chapters deals with the problems of classifying complex solids and with systematic descriptions of the relationships between their structures. This book comprises 13 chapters, with the first presenting a historical perspective by Linus Pauling. The following chapters then go on to discuss quantum theory and crystal chemistry; pseudopotentials and crystal structure; quantum-defect orbital radii and the structural chemistry of simple solids; and a pseudopotential viewpoint of the electronic and structural properties of crystals. Other chapters cover elementary quantitative theory of chemical bonding; the role and significance of empirical and semiempirical correlations; theoretical probes of bonding in the disiloxy group; a comparison of experimental and theoretical bond length and angle variations; the role of nonbonded forces in crystals; molecules within infinite solids; charge density distributions; and some aspects of the ionic model of crystals. This book will be of interest to practitioners in the fields of chemistry, physics, and geology.

One of the motivating questions in materials research today is, how can elements be combined to produce a solid with specified properties? This book is intended to acquaint the reader with established principles of crystallography and cohesive forces that are needed to address the fundamental relationship between the composition, structure and bonding. Starting with an introduction to periodic trends, the book discusses crystal structures and the various primary and secondary bonding types, and finishes by describing a number of models for predicting phase stability and structure. Containing a large number of worked examples, exercises, and detailed descriptions of numerous crystal structures, this book is primarily intended as an advanced undergraduate or graduate level textbook for students of materials science. It will also be useful to scientists and engineers who work with solid materials.

The structural properties of materials play a fundamental role in the determination of their suitability for a specific application. This book is intended as a contribution to the efforts to increase the knowledge of the influence exerted on the properties of materials by their crystalline or amorphous structure. To this aim, some of the materials that are most promising for their use in different technological fields have been studied, namely graphene, titanium oxide, several types of functional metal oxides, porphyrinic crystalline solids, plasma deposited polymers, amorphous silicon, as well as hydrogenated amorphous carbon. These materials have been presented by the authors for their use in different applications, including microelectronics, photonics, and biomedicine.