Conditions for the self-assembling of cluster materials

Clusters with closed electronic shells are highly stable, and this is a robust property with far-reaching implications for cluster abundance, cluster shapes, dynamical response to electric fields and cluster dissociation. Clusters with closed shells are also good candidates for the synthesis of novel materials. The density functional formalism is currently used to investigate the self-assembling of metallic clusters to yield cluster solids. A high intrinsic stability is not the only requirement for expecting a successful assembling, and we investigate additional conditions by performing computer simulations for selected examples. The study of the assembling of hydrogen-doped icosahedral aluminium clusters shows that an optimized relative orientation of each cluster unit with respect to all its neighbour clusters becomes a favourable condition. The analysis of the clustering effects observed in crystalline alloys formed by Pb and alkali metals (tetrahedral Pb-4 clusters surrounded by the alkali cations form in those alloys) provides further insight: coating passivates the clusters and helps to stabilize the assembled material.