Clusters

Abstract

Clusters are small aggregates of atoms or molecules which are transitional forms of matter between atoms or molecules and their corresponding bulk forms. Just as this definition spans an incredibly broad range of clusters from, say, He2 to Na10000, so do the properties of these clusters span a broad range. This chapter attempts to bring order to this diverse cluster kingdom by first sorting them into six general categories. Within each category, the physics and chemistry of the more or less similar cluster species are described. Particular emphasis is placed on the unique properties of clusters owing to their finite size and finite lattice.

This chapter summarizes one of the youngest topics in this volume. Much of what is known is highly qualitative and has not yet been assembled into overarching tables or equations. Thus, this review is best regarded as a progress report on the current knowledge in this rapidly advancing field. Many of the concepts and the language used to discuss clusters are derived from condensed matter physics. The nature of these clusters impels such descriptions.