TABLE OF CONTENTS Mixing two vapors and expanding the mixture [1] produces new clusters that, in the case of metals, are the microscopic analogue of the bulk alloys. In the case of bulk alloys, different stable phases appear for a given pair of metals, characterized by specific crystal structures and usually by fixed concentrations. Transitions to another phase can occur when a critical temperature is reached. Also, some of those phases can be stable over an extended range of atomic concentrations, specially for alloys very rich in one of the components. All this makes the simple book-keeping of the alloy phases of binary systems a whole subject, and compilations of phase diagrams exist. An additional variable enters the picture in the case of finite clusters; this is the number of atoms in the cluster. The field of heteroclusters is then very rich and broad. An example has been presented in Section 3.3.3, where the melting of mixed inert gas clusters was studied using computer simulations as a tool. In this chapter the interest is shifted to mixed clusters of metallic elements, and some representative topics have been selected from the abundant literature.
Supersonic beam expansions of a mixture of lithium and sodium vapors have produced mixed clusters [1]. This is remarkable because Li and Na do not form solid alloys and also present a miscibility gap in the liquid phase. Other salient features are: (a) the magic numbers, corresponding to the most abundant cluster...
