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Using the Car-Parrinello method, we have obtained unforeseen structures for the low-lying isomers of Si₄₅ and other midsized Si clusters. They are formed by two shells of atoms, the outer one (cage) being fullerenelike and inner one (core) consisting of a few atoms saturating dangling bonds. These novel structures provide for the first time a consistent interpretation of the available experimental data, including the reactivity trends and the structural transition at a size of 25 atoms.
Röthlisberger et al. (Mon,) studied this question.