Surface-reconstruction-induced geometries of Si clusters

We discuss a generalization of the surface-reconstruction arguments for the structure of intermediate-size Si clusters, which leads to model geometries for the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57, and 61 (two isomers). The common feature in all these models is a structure that closely resembles the most stable reconstruction of Si surfaces, surrounding a core of bulklike tetrahedrally bonded atoms. We investigate the energetics and the electronic structure of these models through first-principles density-functional theory calculations. These models may be useful in understanding experimental results on the reactivity of Si clusters and their shape as inferred from mobility measurements.