Disorder and Order in Strongly Nonstoichiometric Compounds

long to understand that the phenomena associated with the redistribution of interstitial atoms and structural vacancies in non stoichiometric compounds represent an excellent model of analogous phenomena arising in solid-state systems with mutual substitution of components. Therefore methods of analysis and description proposed and developed for nonstoichiometric compounds are applicable to a number of systems with substitutional disorder. In 1980, when we embarked on this work, ordering in nonstoichiometric compounds was assumed to be a rare and accidental effect, which hardly deserved close attention. Now many people understand that ordering represents a general regular phenomenon in all non stoichiometric compounds. Ordering effects, which were not even mentioned, or were referred to as something insignificant and negligible just 20 years ago, proved to be numerous and comparable in magnitude with the change of properties in the whole homogeneity interval of non stoichiometric compounds. Phase diagrams of binary systems of transition metals with carbon and nitrogen, which remained unchanged from the time they were plotted in 1950-60s and containing one or two nonstoichiometric compounds, were enriched with many ordered phases. Unfortunately, the accumulated experimental and theoretical knowledge has not so far been disseminated widely.

This book embraces the entire range of problems associated with nonstoichiometry, disorder and order in solids. Although dealing primarily with transition metal carbides, nitrides and oxides, the methods and models presented are applicable to all systems with substitutional disorder and they permit a unified approach to the structure, phase diagrams and other physical and chemical properties of these systems. This book will be useful for physicists addressing the problems of order and disorder in solids, for chemists increasingly aware that the majority of natural and synthetic materials are nonstoichiometric, and for crystallographers studying new and unusual crystal structures. Materials scientists using refractory compounds to create novel superhard and tough materials or materials for modern electronics will find essential information on the interplay between structural effects and many different properties of transition metal compounds. More than 1000 references are given in this book.