Materials with layered structures remain an extensively investigated subject in current physics and chemistry. Most of the promising technological applications however deal with intercalation compounds of layered materials. Graphite intercalation compounds have now been known for a long time. Intercalation in transition metal dichalcogenides, on the other hand, has been investigated only recently. The amount of information on intercalated layered materials has increased far beyond the original concept for this volume in the series Physics and Chemistry of Materials with Layered Structures. The large size of this volume also indicates how important this field of research will be, not only in basic science, but also in industrial and energy applications. In this volume, two classes of materials are included, generally investigated by different scientists. Graphite intercalates and intercalates of other inorganic com pounds actually constitute separate classes of materials. However, the similarity between the intercalation techniques and some intercalation processes does not justify this separation, and accounts for the inclusion of both classes in this volume. The first part of the volume deals with intercalation processes and intercalates of transition metal dichalcogenides. Several chapters include connected topics necessary to give a good introduction or comprehensive review of these types of materials. Organic as well as inorganic intercalation compounds are treated. The second part includes contributions concerning graphite intercalates. It should be noted that graphite intercalation compounds have already been mentioned in Volumes I and V."

This monograph is intended to give the reader an appreciation of the wealth of phases, elements and inorganic compounds, which crystallize in layer-type or two dimensional structures. Originally this work was planned as a short review article but the large number of phases made it grow out to the size of a book. As is evident from the arrangement of the chapters our point of view was gradually transmuting from geometric to chemical. Moreover, the decision about the compounds that should be discussed was taken only during the course of the work, as is partly evident from the sequence of the references. For chemical or geometrical reason we have included also certain layered chain and molecular structures as well as some layered structures whose layers are linked by hydrogen bonds, thus are in fact three-dimensional. Instead of writing only a review with pseudo-scientific interpretations that later turn out to be wrong anyway we thought it more profitable to include the crystallographic data which are scattered in various original articles and hand books but never in one single volume. We have transcribed many of the data in order to make them correspond with the standard settings of the International Tables for X-Ray Crystallography. The figures are consistent with the data given in the tables. We apologize for errors and hope that their number is at a reasonably low level in spite of the time pressure."

In Bird of Passage by Rudolf Peierls, we find a paragraph in which he de scribes his Cambridge days in the 1930s: On these relativistic field theory] problems my main contacts were Dirac, and the younger theoreticians. These included in particular Nevill (now Sir Nevill) Mott, perhaps the friendliest among many kind and friendly people we met then. Professor Kamimura became associated with Sir Rudolf Peierls in the 1950s, when he translated, with his colleagues, Peierls's 1955 textbook, Quantum Theory of Solids, into Japanese. This edition, to which Sir Rudolf himself contributed a preface, benefitted early generations of Japanese solid state physicists. Later in 1974/5, during a sabbatical year spent at the Cavendish Laboratory, Professor Kamimura met and began a long association with Sir Nevill Mott. In particular, they developed ideas for disordered systems. One of the outcomes is a paper coauthored by them on ESR-induced variable range hopping in doped semiconductors. A series of works on disordered systems, together with those on two-dimensional systems, have served as building blocks for Physics of Interacting Electrons in Disordered Systems, in the International Series of Monographs on Physics, coauthored by Aoki and published in 1989 by the Oxford University Press. Soon after Professor Kamimura obtained a D. Sc. in 1959 for the work on the ligand field theory under the supervision ofMasao Kotani, his strong con nections in the international physical community began when he worked at the Bell Telephone Laboratories in 1961/64."

In Bird of Passage by Rudolf Peierls, we find a paragraph in which he de scribes his Cambridge days in the 1930s: On these relativistic field theory] problems my main contacts were Dirac, and the younger theoreticians. These included in particular Nevill (now Sir Nevill) Mott, perhaps the friendliest among many kind and friendly people we met then. Professor Kamimura became associated with Sir Rudolf Peierls in the 1950s, when he translated, with his colleagues, Peierls's 1955 textbook, Quantum Theory of Solids, into Japanese. This edition, to which Sir Rudolf himself contributed a preface, benefitted early generations of Japanese solid state physicists. Later in 1974/5, during a sabbatical year spent at the Cavendish Laboratory, Professor Kamimura met and began a long association with Sir Nevill Mott. In particular, they developed ideas for disordered systems. One of the outcomes is a paper coauthored by them on ESR-induced variable range hopping in doped semiconductors. A series of works on disordered systems, together with those on two-dimensional systems, have served as building blocks for Physics of Interacting Electrons in Disordered Systems, in the International Series of Monographs on Physics, coauthored by Aoki and published in 1989 by the Oxford University Press. Soon after Professor Kamimura obtained a D. Sc. in 1959 for the work on the ligand field theory under the supervision ofMasao Kotani, his strong con nections in the international physical community began when he worked at the Bell Telephone Laboratories in 1961/64."

This monograph is intended to give the reader an appreciation of the wealth of phases, elements and inorganic compounds, which crystallize in layer-type or two dimensional structures. Originally this work was planned as a short review article but the large number of phases made it grow out to the size of a book. As is evident from the arrangement of the chapters our point of view was gradually transmuting from geometric to chemical. Moreover, the decision about the compounds that should be discussed was taken only during the course of the work, as is partly evident from the sequence of the references. For chemical or geometrical reason we have included also certain layered chain and molecular structures as well as some layered structures whose layers are linked by hydrogen bonds, thus are in fact three-dimensional. Instead of writing only a review with pseudo-scientific interpretations that later turn out to be wrong anyway we thought it more profitable to include the crystallographic data which are scattered in various original articles and hand books but never in one single volume. We have transcribed many of the data in order to make them correspond with the standard settings of the International Tables for X-Ray Crystallography. The figures are consistent with the data given in the tables. We apologize for errors and hope that their number is at a reasonably low level in spite of the time pressure."

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."