MAGIC NUMBERS OF SILICON CLUSTERS

A structural model for intermediate-size silicon clusters is proposed that is able to generate unique structures without any dangling bonds. This structural model consists of a bulklike core of five atoms surrounded by a fullerenelike surface. Reconstruction of the ideal fullerene geometry results in the formation of crown atoms surrounded by -bonded dimers. This model yields unique structures for Si33, Si39, and Si45 clusters without any dangling bonds and hence explains why these clusters are the least reactive towards chemisorption of ammonia. Finally, reagent-specific chemisorption reactivities observed experimentally are explained based on the electronic structures of the reagents. © 1994 The American Physical Society.