Metal Cluster Compounds

Abstract

Studies of metal clusters, i.e., small metal particles containing a number (n) of atoms in the range n = 10 − 10000, are of interest not only for fundamental science but also for potential applications as e.g. in the fields of catalysis, microelectronics, or magnetic recording media. Fundamental scientific questions are mostly related to the so-called quantum-size effects [1]. Basically, for such small particles the cluster size becomes comparable to characteristic physical lengthscales such as the De Broglie wavelength of an electron at the Fermi energy of the (bulk) metal, the superconducting coherence length, the wavelengths of lattice waves (phonons) or magnetic waves (magnons), etc. As a consequence, the familiar bulk behavior is lost and the physical properties become predominated by quantum mechanical phenomena, in particular the wave-nature of the electron. The terms “quantum-wells” or “quantum-dots” are used for such confined systems. It is expected that these size-effects may ultimately be exploited to create materials with novel magnetic, optical, dielectric, or electronic transport properties. We note that for good metals the Fermi wavelength is of the order of 1 nm, whereas for semiconductors it can become several orders of magnitude larger.