Effect of surface reconstruction on stability and reactivity of Si clusters

It is proposed that magic number Si clusters of intermediate size correspond to structures in which exactly all surface atoms participate in reconstructions similar to bulk-Si surfaces. Models are given for the experimentally observed stable clusters of 33 and 45 atoms, which display features similar to the 7×7 and 2×1 reconstructions of the Si(111) surface. The nature of bonding in the energy-optimized atomic geometries is revealed, through first-principles electronic structure calculations, to be covalent. © 1990 The American Physical Society.