Chemistry

Gilding the Superatom Model

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Science  18 Jul 2008:
Vol. 321, Issue 5887, pp. 319
DOI: 10.1126/science.321.5887.319c

When metal atoms bind together in the gas phase to form clusters, they tend to gather preferentially in certain discrete numbers. This tendency has been rationalized with a superatom model, in which the addition of atoms to a cluster is analogous to the filling of valence electron shells in atoms themselves, so that when a critical number of atoms donate electrons to the cluster, they effectively form the equivalent of a noble gas configuration. Extending the model to clusters crystallized in solution seemed more complicated, given the requirement in that context of coordinating ligands for steric protection. However, Walter et al. show, using density functional theory, that the superatom model straightforwardly accounts for the particular stability of two crystallographically characterized gold clusters, the thiolate-coordinated Au102 and phosphine/halide-coordinated Au39, as well as several smaller examples. The theory also predicts stability of 44- and 75-membered clusters that are yet to be fully structurally characterized. — JSY

Proc. Natl. Acad. Sci. U.S.A. 105, 9157 (2008).

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