FIRST-PRINCIPLES STUDY ON B(12) CLUSTERS IN SI

The ab initio calculation is reported on the B-12 clusters in crystall ine Si, whose existence has:been recently suggested experimentally. We investigated the atomic and the electronic structures for two possibl e configurations of B-12 clusters; icosahedron and cubo-octahedron. We found that both of the clusters capture the valence electrons, which results in the generation of an unoccupied level in the valence band o f crystalline Si. It was also found that the icosahedral B-12 in Si is more stable than the cube-octahedral B-12, although the symmetry of a cubo-octahedron (O-h) is more favorable to crystalline Si than that o f an icosahedron (I-h). The calculated results suggest that the experi mentally observed B-12 clusters take the icosahedral configuration.