Structure and bonding of small semiconductor clusters.

We calculate the geometrical and electronic structure of small Sin, Sin +, and Sin clusters up to sites n = 14 within a combined tight-binding-density-functional-theory scheme. Especially stable structures for n = 6 and 10 coincide with observed abundancies in the experimental mass spectra. All equilibrium structures are found to be close packed, with a different bonding than found in the bulk fragments. A transition to bulklike open structures is estimated to occur at cluster sizes n "" 102_103.