Metal Clusters At Surfaces

Due to the interaction with the contact medium, the properties of clusters may change or even disappear. Thus the physics of cluster-on-surface systems -- the main subject of this book -- is of fundamental importance. The book addresses a wide audience, from the newcomer to the expert. Starting from fundamental concepts of adsorbate-surface interactions, the modification of electronic properties through electron confinement, and concepts of cluster production, it elucidates the distinct properties of the new metallic nanostructures.

Metal-ligand interactions are currently being studied in different fields, from a variety of points of view, and recent progress has been substantial. Whole new classes of compounds and reactions have been found; an arsenal of physical methods has been developed; mechanistic detail can be ascertained to an increasingly minute degree; and the theory is being developed to handle systems of ever-growing complexity. As usual, such multidisciplinarity leads to great opportunities, coupled with great problems of communication between specialists. It is in its promotion of interactions across these fields that Metal-Ligand Interactions: From Atoms, to Clusters, to Surfaces makes its timely contribution: the tools, both theoretical and experimental, are highly developed, and fundamental questions remain unanswered. The most fundamental of these concerns the nature of the microscopic interactions between metal atoms (clusters, surfaces) and ligands (atoms, molecules, absorbates, reagents, products) and the changes in these interactions during physical and chemical transformation. In Metal-Ligand Interactions, leading experts discuss the following, vital aspects: ab initio theory, semi-empirical theory, density functional theory, complexes and clusters, surfaces, and catalysis.

It is widely recognized that an understanding of the physical and chemical properties of clusters will give a great deal of important information relevant to surface and bulk properties of condensed matter. This relevance of clusters for condensed matter is one of the major motivations for the study of atomic and molecular clusters. The changes of properties with cluster size, from small clusters containing only a few atoms to large clusters containing tens of thousands of atoms, provides a unique way to understand and to control the development of bulk properties as separated units are brought together to form an extended system. Another important use of clusters is as theoretical models of surfaces and bulk materials. The electronic wavefunctions for these cluster models have special advantages for understanding, in particular, the local properties of condensed matter. The cluster wavefunctions, obtained with molecular orbital theory, make it possible to relate chemical concepts developed to describe chemical bonds in molecules to the very closely related chemical bonding at the surface and in the bulk of condensed matter. The applications of clusters to phenomena in condensed matter is a cross-disciplinary activity which requires the interaction and collaboration of researchers in traditionally separate areas. For example, it is necessary to bring together workers whose background and expertise is molecular chemistry with those whose background is solid state physics. It is also necessary to bring together experimentalists and theoreticians.

Metal-Oxygen Clusters is the first book, providing an overview of the surface chemistry and catalytic properties of heteropoly oxometalates. After a brief look at the early knowledge of heteropoly oxometalates, the book discusses the synthesis, characterization, structure, bulk properties and stability of these materials. The remainder and the largest portion of the book explores the properties of these solids as catalysts in acid-catalyzed and oxidation processes in supported or unsupported forms. The book provides an up-to-date review of the methods for synthesizing heteropoly oxometalates of Keggin structure, techniques from spectroscopic through electrochemical to elemental analysis for their characterization and the current information on their structure, bulk properties and their stabilities at high temperatures and under acid and alkaline conditions. The book discusses the materials employed as supports for the title solid and the results of the examination of the supported materials. Methods for the identification of the nature and source of the two catalytic functions, the acidic and oxidative properties, of the heteropoly oxometalates are reviewed and discussed. The use of both the supported and unsupported heteropoly oxometalates as catalysts in acidity-requisite processes ranging from methanol conversion to hydrocarbons to ring-expansion and contraction processes and in oxidation processes from methane cyclohexane are described and related to the aforementioned properties.

The analogy between the chemistry of molecular transition metal clusters and the processes of chemisorption and catalysis at metal surfaces (the Cluster Surface analogy) has for a number of years provided an interplay between experimental and theoretical inorganic and physical chemists. This collaborative approach has born fruit in the use of well defined modes of metal-ligand bonding in discrete molecular clusters, models for metal-ligand binding on surfaces. Some of the key topics discussed in The Synergy between Dynamics and Reactivity at Clusters and Surfaces are: (1) Mechanisms of the fluxional behaviour in clusters in the liquid phase and the connections with diffusion processes on extended surfaces. The role of metal-metal bond breaking in diffusion. (2) Analogies in the structure of chemisorbed species and related ligands on metallic clusters. (3) Analogies between benzene surface chemistry on extended metal surfaces and on metal surfaces in molecular cluster compounds with particular reference to structural distortions. (4) The role of mobile precursors for dissociation of chemisorption on extended metals and on clusters. Are there analogies in the ligand attachment during cluster compound synthesis? (5) The role of defect sites on metal surfaces in catalyzing chemical reactions and the connection to the special bonding properties of sites on metal clusters having lowest metal-metal coordination. (6) The size of metal clusters needed to mimic surface phenomena on bulk metal surfaces. Different sites needed for different phenomena.

"For the first time, this book unites the theory, experimental techniques and computational tools used to describe the diffusion of atoms, molecules and nanoparticles across metal surfaces. Starting with an outline of the formalism that describes diffusion on surfaces, the authors guide the reader through the principles of atomic movement, before moving on to diffusion under special circumstances, such as the presence of defects or foreign species. With an initial focus on the behaviour of single entities on a surface, later chapters address the movement of clusters of atoms and the interactions between adatoms. While there is a special emphasis on experimental work, attention is paid to the increasingly valuable contributions theoretical work has made in this field. This book has wide interdisciplinary appeal and is ideal for researchers in solid state physics, chemistry as well as materials science, and engineering"--Provided by publisher.

Understanding the electronic structure of solids is a basic part of theoretical investigation in physics. Application of investigative techniques requires the solid under investigation to be "periodic." However, this is not always the case. This volume addresses three classes of "non-periodic" solids currently undergoing the most study: alloys, surfaces and clusters. Understanding the electronic structure of these systems is fundamental not only for the basic science, but also constitutes a very important step in various technological aspects, such as tuning their stabilities, chemical and catalytic reactivities and magnetism. Expert practitioners give an up-to-date account of the field with enough detailed background so that even a newcomer can follow the development. The theoretical framework is discussed in addition to the present status of knowledge in the field. Electronic Structure of Alloys, Surfaces and Clusters also includes an extensive bibliography which provides a comprehensive reading list of work on the topic.