Theoretical and experimental work on solids with low-dimensi℗Ư onal cooperative phenomena has been rather explosively expanded in the last few years, and it seems to be quite fashionable to con℗Ư tribute to this field, especially to the problem of one-dimensional metals. On the whole, one could divide the huge amount of recent investigations into two parts although there is much overlap bet℗Ư ween these regimes, namely investigations on magnetic exchange interactions constrained to mainly one or two dimensions and, secondly, work done on Id metallic solids or linear chain compounds with Id delocalized electrons. There is, of course, overlap from one extreme case to the other with these solids and in some rare cases both phenomena are studied on one and the same crystal. In fact, however, most of the scientific groups in this area could be associated roughly with one of these categories and, in addition, a separation between theoreticians and experimentalists in each of these groups leads to a further splitting of interests although many theories about these solids have been tested by experimenta℗Ư lists. Nevertheless, more cooperation and understanding between scientists working on low-dimensional cooperative phenomena should appreciably stimulate further development. With a better inderdis℗Ư ciplinary understanding, new ideas could possibly help chemists in synthesizing tailor-cut solids. This would in return give experi℗Ư mentalists new phenomena to examine and finally would stimulate new theoretical work.

Proceedings of the NATO Advanced Study Institute, Tomar, Portugal, August 26-September 7, 1979

Low-dimensional magnetism physics involves the search for new magnetic compounds and improving their characteristics to meet the needs of innovative technologies. A comprehensive overview of key materials, their formulation data and characteristics are detailed by the author. Key selling features: Explores dominant mechanisms of magnetic interaction to determine the parameters of exchange interactions in new magnetic materials. Describes how magnetism and superconductivity not only compete, but also "help" each other. Details characteristics of key materials in the magnetic subsystem. Results of several internationally renowned research groups are included and cited. Suitable for a wide range of readers in physics, materials science, and chemistry interested in the problems of the structure of matter.

During the past few years there has been intense research activity in the design, synthesis, and characterization of materials which are formed from molecular precursors, and which have high or metal-like electrical conductivities, i.e. dcr/dT

This volume represents the written account of the NATO Advanced Study Institute "Lower-Dimensional Systems and Molecular Electronics" held at Hotel Spetses, Spetses Island, Greece from 12 June to 23 June 1989. The goal of the Institute was to demonstrate the breadth of chemical and physical knowledge that has been acquired in the last 20 years in inorganic and organic crystals, polymers, and thin films, which exhibit phenomena of reduced dimensionality. The interest in these systems started in the late 1960's with lower-dimensional inorganic conductors, in the early 1970's with quasi-one-dimensional crystalline organic conductors. which by 1979 led to the first organic superconductors, and, in 1977, to the fITSt conducting polymers. The study of monolayer films (Langmuir-Blodgett films) had progressed since the 1930's, but reached a great upsurge in . the early 1980's. The pursuit of non-linear optical phenomena became increasingly popular in the early 1980's, as the attention turned from inorganic crystals to organic films and polymers. And in the last few years the term "moleculw' electronics" has gained ever-increasing acceptance, although it is used in several contexts. We now have organic superconductors with critical temperatures in excess of 10 K, conducting polymers that are soluble and processable, and used commercially; we have films of a few monolayers that have high in-plane electrical conductivity, and polymers that show great promise in photonics; we even have a few devices that function almost at the molecular level.

It has been a decade since two seminal reviews demonstrated that mixed-valence compounds share many unique and fascinating features. The insight pro vided by those early works has promoted a great deal of both experimental and theoretical study. As a result of extensive efforts, our understanding of the bonding and properties of mixed-valence compounds has advanced substantially. There has been no compre hensive treatment of mixed-valence compounds since 1967, and the meeting convened at Oxford in September, 1979, provided a unique opportunity to examine the subject and its many ramifications. Mixed-valence compounds play an important role in many fields. Although the major impact of the subject has been in chemistry, its importance has become increasingly clear in solid state physics, geology, and biology. Extensive interest and effort in the field of molecular metals has demonstrated that mixed-valency is a prerequisite for high elec trical conductivity. The intense colors of many minerals have been shown to be due to mixed-valency, and the electron-transfer properties of certain mixed-valence metalloproteins are important in biological processes. Experts from all of these areas participated in this meeting, and the truly interdisciplinary nature of the subject made it a unique learning experience for all in attendance.

Linear chain substances span a large cross section of contemporary chemistry ranging from covalent polymers, to organic charge transfer com plexes to nonstoichiometric transition metal coordination complexes. Their commonality, which coalesced intense interest in the theoretical and exper imental solid state physics/chemistry communities, was based on the obser vation that these inorganic and organic polymeric substrates exhibit striking metal-like electrical and optical properties. Exploitation and extension of these systems has led to the systematic study of both the chemistry and physics of highly and poorly conducting linear chain substances. To gain a salient understanding of these complex materials rich in anomalous aniso tropic electrical, optical, magnetic, and mechanical properties, the conver gence of diverse skills and talents was required. The constructive blending of traditionally segregated disciplines such as synthetic and physical organic, inorganic, and polymer chemistry, crystallography, and theoretical and ex perimental solid state physics has led to the timely development of a truly interdisciplinary science. This is evidenced in the contributions of this monograph series. Within the theme of Extended Linear Chain Compounds, experts in important, but varied, facets of the discipline have reflected upon the progress that has been made and have cogently summarized their field of specialty. Consequently, up-to-date reviews of numerous and varied aspects of "extended linear chain compounds" have developed. Within these vol umes, numerous incisive contributions covering all aspects of the diverse linear chain substances have been summarized.