Structure and stability of B6, B+6 and B-6 clusters

We investigated various isomers of B-6, B-6(+), and B-6(-) clusters with ab initio[Hartree-Fock (HF), MP2)] and density functional theory (DFT) methods. Ten B-6 isomers, 6 B-6(+) isomers, and 6 B-6(-) isomers are determined to be local minima on their potential energy hypersurfaces by the HF, B3LYP, B3PW91, and MP2 methods. Fourteen of these structures are first reported. The most stable neutral B-6 cluster is the capped pentagonal pyramid (C-5v), in agreement with the results reported previously. Hexagon B-6(+) (C-2h) isomer and fan-shaped B-6(-) (C-2v) isomer are found to be the most stable on the cationic and anionic energy hypersurfaces, respectively. Natural bond orbital analysis suggests that there are three-centered bonds in the most stable B-6 neutral and ionic clusters. The multicentered bonds are responsible for the special stability of the lowest-energy isomer. (C) 2003 Wiley Periodicals, Inc.