In the last ten years, the chemistry and physics of materials with layered structures became an intensively investigated field in the study of the solid state. Research into physical properties of these crystals and especially investigations of their physical anisotropy related to the structural anisotropy has led to remarkable and perplexing results. Most of the layered materials exist in several polytypic modifications and can include stacking faults. The crystal structures are therefore complex and it became apparent that there was a great need for a review of the crystallographic data of materials approximating two-dimensional solids. This second volume in the series 'Physics and Chemistry of Materials with Layered Structures' has been written by specialists of different classes of layered materials. Structural data are reviewed and the most important relations between the structure and the chemical and physical properties are emphasized. The first three contributions are devoted to the transition metal dichalcogenides whose physical properties have been investigated in detail. The crystallographic data and crystal growth conditions are presented in the first paper. The second paper constitutes an incisive review of the phase transformations and charge density waves which have been observed in the metallic dichalcogenides. In two contributions the layered structures of newer ternary compounds are de scribed and the connection between structure and non-stoichiometry is discussed.

The goal of the series Physics and Chemistry of Materials with Layered Structures is to give a critical survey of our present knowledge on a large family of materials which can be described as solids containing molecules which in two dimensions extend to infinity and which are loosely stacked on top of each other to form three dimensional crystals. Of course, the physics and chemistry of these crystals are specific chapters in ordinary solid state science, and many a scientist hunting for new phenomena has in the past been disappointed to find that materials with layered structures are not entirely exotic. Their electron and phonon states are not two dimensional, and the high hopes held by some for spectacular dimensionality effects in superconductivity were shattered. Nevertheless, the structural features and their physical and chemical consequences singularize layered structures sufficiently to make them a fascinating subject of research. This is all the more true since they are met in insulators and semiconductors as well as in normal and superconducting metals. Although for the time being the series is intentionally limited to cover inorganic materials only, the many known organic layered structures may well be the subject of future volumes. Among the noteworthy peculiarities of layered structures, we mention specific growth mechanisms and crystal habits. Polytypism is very common and it is fasci nating indeed to find up to 240 different polytypes in the same chemical substance.

'This is a book for crystal chemistry lovers written by one of the pioneers of solid-state chemistry.'MRS BulletinDevoted to a diverse group of solid state scientists, the book has two objectives, both relating to structural chemistry: (i) a progressive analytic familiarization with the main parameters that govern the organization of crystallized matter and related crystal structures, (ii) a study of what are the various ways to 'read' a structure far beyond its representation in scientific articles. Hence, the reader will, from numerous examples illustrated in color, analyze what are the main characteristics of these structures, from their geometric characteristics, their coordination polyhedra, their connections with the resulting dimensionalities of these solids, including also the defects they exhibit, before looking at possibilities to classify structures, within which recurrence laws can emerge.Chemists are required to understand the potentials of a new structure for becoming future materials scientists. The first part of the book is by no means a database for known structures, but facilitates a progressive understanding of the organization of the solid state. With these tools in hand, the reader is invited in the later part of the book to analyze new structures, and to also use new concepts for viewing structures in a more synthetic way for the future. Such new vision is already leading to the creation of completely new solids with outstanding characteristics that find applications in societal problems concerning energy, energy savings, environment and health.The content is not exclusively academic but relates to the creation of innovative materials, through a more physical approach, that might condition the future of materials.

Index of layered materials