P. Jena – författare

Hydrogen is the smallest impurity atom that can be implanted in a metallic host. Its small mass and strong interaction with the host electrons and nuclei are responsible for many anomalous and interesting solid state effects. In addition, hydrogen in metals gives rise to a number of technological problems such as hydrogen embrittlement, hydrogen storage, radiation hardening, first wall problems associated with nuclear fusion reactors, and degradation of the fuel cladding in fission reactors. Both the fundamental effects and applied problems have stimulated a great deal of inter­ est in the study of metal hydrogen systems in recent years. This is evident from a growing list of publications as well as several international conferences held in this field during the past decade. It is clear that a fundamental understanding of these problems re­ quires a firm knowledge of the basic interactions between hydrogen, host metal atoms, intrinsic lattice defects and electrons. This understanding is made particularly difficult by hyrogen''s small mass and by the large lattice distortions that accompany the hydrogenation process. The purpose of the "International Symposium on the Electronic Structure and Properties of Hydrogen in Metals" held in Richmond, Virginia, March 4-6, 1982 was to increase our fundamental under­ standing of hydrogen in metals. Such knowledge is essential in solving technologically important questions. The symposium con­ sisted of twenty-two invited papers and seventy-two contributed poster presentations and attracted nearly 150 participants from thirteen countries. The proceedings of this symposium constitute this book.

Hydrogen is the smallest impurity atom that can be implanted in a metallic host. Its small mass and strong interaction with the host electrons and nuclei are responsible for many anomalous and interesting solid state effects. In addition, hydrogen in metals gives rise to a number of technological problems such as hydrogen embrittlement, hydrogen storage, radiation hardening, first wall problems associated with nuclear fusion reactors, and degradation of the fuel cladding in fission reactors. Both the fundamental effects and applied problems have stimulated a great deal of inter­ est in the study of metal hydrogen systems in recent years. This is evident from a growing list of publications as well as several international conferences held in this field during the past decade. It is clear that a fundamental understanding of these problems re­ quires a firm knowledge of the basic interactions between hydrogen, host metal atoms, intrinsic lattice defects and electrons. This understanding is made particularly difficult by hyrogen's small mass and by the large lattice distortions that accompany the hydrogenation process. The purpose of the "International Symposium on the Electronic Structure and Properties of Hydrogen in Metals" held in Richmond, Virginia, March 4-6, 1982 was to increase our fundamental under­ standing of hydrogen in metals. Such knowledge is essential in solving technologically important questions. The symposium con­ sisted of twenty-two invited papers and seventy-two contributed poster presentations and attracted nearly 150 participants from thirteen countries. The proceedings of this symposium constitute this book.

Recent advances in experimental techniques now enable researchers to produce in a laboratory clusters of atoms of desired composition from any of the elements of the periodic table. This has created a new area of research into novel materials since clusters cannot be regarded either as a "large" molecule or as a fragment of the bulk. Both experimental and theoretical studies are revealing unusual properties that are not ob­ served in solid state environments. The structures of micro-clusters are found to be significantly distorted from the most symmetric arrangement, some even exhibiting pentagonal symmetry commonly found in icosahedric structures. The unusual stability of certain clusters, now described as "magic number species", shows striking similarities with the nuclear shell structure. The relative stabilities of clusters depend not only on the composition of the clusters but also on their charged states. The studies on spontaneous fragmentation of mUltiply charged clusters, commonly referred to as Coulomb explosion, illustrate the role of electronic bonding mechanisms on stability of clusters. The effect of foreign atoms on geometry and stability of clusters and the interaction of gas atoms with clusters are showing promise for an indepth understanding of chemisorption and catalysis. The magnetic and optical properties are dependent not only on cluster size but also on its geometry. These findings have the potential for aiding industry in the area of micro-electronics and catalysis.

Recent advances in experimental techniques now enable researchers to produce in a laboratory clusters of atoms of desired composition from any of the elements of the periodic table. This has created a new area of research into novel materials since clusters cannot be regarded either as a "large" molecule or as a fragment of the bulk. Both experimental and theoretical studies are revealing unusual properties that are not ob­ served in solid state environments. The structures of micro-clusters are found to be significantly distorted from the most symmetric arrangement, some even exhibiting pentagonal symmetry commonly found in icosahedric structures. The unusual stability of certain clusters, now described as "magic number species", shows striking similarities with the nuclear shell structure. The relative stabilities of clusters depend not only on the composition of the clusters but also on their charged states. The studies on spontaneous fragmentation of mUltiply charged clusters, commonly referred to as Coulomb explosion, illustrate the role of electronic bonding mechanisms on stability of clusters. The effect of foreign atoms on geometry and stability of clusters and the interaction of gas atoms with clusters are showing promise for an indepth understanding of chemisorption and catalysis. The magnetic and optical properties are dependent not only on cluster size but also on its geometry. These findings have the potential for aiding industry in the area of micro-electronics and catalysis.

This book covers the synthesis and characterization of materials with atomic dimension. These include atomic clusters, nanostructured materials, multilayers and one-dimensional arrays. The effect of reduced size and dimensionality on electronic, magnetic, optical and catalytic properties and the technological prospects of atomically engineered materials is highlighted.

This book deals with the evolution of the properties of clusters, nanostructures and cluster-based materials, with emphasis on the role of the interface. These materials are characterized by reduced size, dimension and symmetry, and possess many novel properties that are not commonly seen in their bulk phases. The topics include synthesis, nucleation, growth, characterization, atomic and electronic structure, dynamics, ultra-fast spectroscopy, stability; electrical, magnetic, optical, thermodynamic and catalytic properties of clusters (free and supported); cluster materials (self-assembled, ligated and embedded); nanostructures (quantum dots, wells and corrals; nanotubes and wires; colloidal and biological materials) and nano-technology (electronic, magnetic and optical devices). In addition to presenting the current status of the field, the book discusses outstanding problems and future directions.