Small metal particles theoretical methods

The basic question to which we require an answer is how small may a metal particle become before it loses its metallic properties Or conversely, in the growth of a metallic cluster, at what point does the electronic structure closely approximate to that of the bulk metal Though the questions appear simple the answers are not. This is partly because the many properties that may be used to characterize the metallic state are differently related to cluster size, so that one may be achieved at a much earlier stage in cluster growth than another. Moreover, if one property is arbitrarily selected as a criterion, the various available theoretical methods for the calculation of that property may differ in their predictions as to when, during cluster growth, the metallic state is achieved. 

This review is concerned with the advances in our understanding of chemical problems that have occurred as a result of developments in computational electrodynamics, with an emphasis on problems involving the optical properties of nanoscale metal particles. In addition, in part of the review we describe theoretical methods that mix classical electrodynamics with molecular quantum mechanics, and which thereby enable one to describe the optical properties of molecules that interact with nanoparticles. Our focus will be on linear optical properties, and on the interaction of electromagnetic fields with materials that are large enough in size that the size of the wavelength matters. We will not consider intense laser fields, or the interaction of fields with atoms or small molecules. 

Material particles consisting of a few to a few thousand atoms are called clusters. Cluster properties can have dramatic size and shape dependence. Clusters can serve as building blocks for new materials and electronic devices. Hence clusters of metals, semiconductors, ionic solids, rare gases, and small molecules have been studied using both theoretical and experimental methods. Atomic and molecular clusters [1] are held together by hydrogen bonds [2] or by relatively weak intermolecular forces [3, 4]. 

Within this project, experimental results and theoretical models were combined to describe and predict the stabilization of metal oxide nanoparticles using small molecules. For the synthesis of well-defined highly crystalline metal oxide nanoparticles as model systems, the non-aqueous sol-gel synthesis was employed. This synthesis is an easily reproducible method that enables the control of the particle size as well as the morphology of the particles. To describe and model the stabilization with short molecules, such as amines or carboxylic acids, ITO and Zr02 nanoparticles were selected as model systems. To prevent influences of the in situ stabilization... 

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