This volume on Clusters brings together contributions from a large number of specialists. A central element for all contributions is the use of advanced computational methodologies and their application to various aspects of structure, reactivity and properties of clusters. The size of clusters varies from a few atoms to nanoparticles.
Atomic clusters are aggregates of atoms containing a few to several thousand atoms. Due to the small size of these pieces of matter, the properties of atomic clusters in general are different from those of the corresponding material in the macroscopic bulk phase. This monograph presents the main developments of atomic clusters and the current status of the field. The book treats different types of clusters with very different properties: clusters in which the atoms or molecules are tied by weak van der Waals interactions, metallic clusters, clusters of ionic materials, and network clusters made of typical covalent elements. It includes methods of experimental cluster synthesis as well as the structural, electronic, thermodynamic and magnetic properties of clusters, covering both experiments and the theoretical work that has led to our present understanding of the different properties of clusters. The question of assembling nanoclusters to form solids with new properties is also considered. Having an adequate knowledge of the properties of clusters can be of great help to any scientist working with objects of nanometric size. On the other hand, nanoclusters are themselves potentially important in fields like catalysis and nanomedicine.
Atomic clusters are aggregates of atoms containing a few to several thousand atoms. Due to the small size of these pieces of matter, the properties of atomic clusters in general are different from those of the corresponding material in the macroscopic bulk phase. This monograph presents the main developments of atomic clusters and the current status of the field. The book treats different types of clusters with very different properties: clusters in which the atoms or molecules are tied by weak van der Waals interactions, metallic clusters, clusters of ionic materials, and network clusters made of typical covalent elements. It includes methods of experimental cluster synthesis as well as the structural, electronic, thermodynamic and magnetic properties of clusters, covering both experiments and the theoretical work that has led to our present understanding of the different properties of clusters. The question of assembling nanoclusters to form solids with new properties is also considered.Having an adequate knowledge of the properties of clusters can be of great help to any scientist working with objects of nanometric size. On the other hand, nanoclusters are themselves potentially important in fields like catalysis and nanomedicine./a
This book covers the continually expanding field of metal nanoparticles and clusters, in particular their size-dependent properties and quantum phenomena. The approaches to the organization of atoms that form clusters and nanoparticles have been advancing rapidly in recent times. These advancements are described through a combination of experimental and computational approaches and are covered in detail by the authors. Recent highlights of the various emerging properties and applications ranging from plasmonics to catalysis are showcased.
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.
Chemical structure and bonding. The scope of the series spans the entire Periodic Table and addresses structure and bonding issues associated with all of the elements. It also focuses attention on new and developing areas of modern structural and theoretical chemistry such as nanostructures, molecular electronics, designed molecular solids, surfaces, metal clusters and supramolecular structures. Physical and spectroscopic techniques used to determine, examine and model structures fall within the purview of Structure and Bonding to the extent that the focus is on the scientific results obtained and not on specialist information concerning the techniques themselves. Issues associated with the development of bonding models and generalizations that illuminate the reactivity pathways and rates of chemical processes are also relevant. The individual volumes in the series are thematic. The goal of each volume is to give the reader, whether at a university or in industry, a comprehensive overview of an area where new insights are emerging that are of interest to a larger scientific audience.
Synthesizing specific clusters as a component of useful nanostructures or controlling them as an assembly of nanocomposites is the ultimate aim. In order to understand how to synthesize individual clusters or to investigate its properties, a variety of first-principles and empirical calculations and related computer simulations have been performed alongside numerous experiments.
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.
It is well known that the optical properties of nanoparticles of noble metals, in particular gold and silver, deviate strongly from those of macroscopic metals. For sizes between ten and a few hundred nanometers, they are dominated by surface plasmons (SPs) described by purely classical models. On the other hand, clusters of a few tens of atoms behave like quantum systems inducing new optical behaviors. The structure of the nanoparticles and the dielectric environment can affect the optical properties. In this thesis I used a scanning transmission electron microscope (STEM) fitted with an electron energy loss spectrometer (EELS) to measure, in parallel, the optical and structural properties of individual nanoparticles. I present how complementary experiments (STEM-EELS and optical absorption) on sizeselected small silver nanoparticles embedded in silica yield at first inconsistent results: while optical absorption shows no size-effect in the range between only a few atoms and ~10 nm, a clear spectral shift is observed in STEM-EELS technique. Our quantitative interpretation, based on a mixed classical/quantum model which takes into account all the relevant quantum effects, resolves the apparent contradictions, not only within our experimental data, but also in the literature. Our comprehensive model describes how the local environment is the crucial parameter controlling the manifestation or absence of quantum size effects. Secondly, I was interested in the purely classical region through lithographed structures of a few hundred nanometers. Although triangular plasmonic cavities have been widely studied in the literature, a classification in terms of plasmonic modes of breathing and edge was missing. In this study, experimental STEM-EELS results, analytical models and classical simulations enabled us to describe the nature of the different modes.
Cluster Materials is the fourth volume of the highly successful series Advances in Metal and Semiconductor Clusters. In this volume the focus is on the properties of clusters which determine their potential applications as new materials. Metal and semiconductor clusters have been proposed as precursors for materials or as actual materials since the earliest days of cluster research. In the last few years, a variety of techniques have made it possible to produce clusters in sizes varying from a few atoms up to several thousand atoms. While some measurements are performed in the gas phase on non-isolated clusters, many cluster materials can now be isolated in macroscopic quantities and more convenient studies of their properties become possible. In this volume the authors focus on measurement of optical, electronic, magnetic, chemical and mechanical properties of clusters or of cluster assemblies. All of these properties must fall into acceptable ranges of behaviour before useful materials composed of clusters can be put into practical applications. As evidenced by the various work described here, the realisation of practical products based on cluster materials seems to be approaching rapidly.
