Ab initio density functional investigation of B₂₄ clusters: rings, tubes, planes, and cages

Abstract

We investigate the equilibrium geometries and the systematics of bonding in various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular dynamics within the framework of density functional theory. The isomers studied are the rings, convex and quasiplanar structures, the tubes, and closed structures. A staggered double ring is found to be the most stable structure among the isomers studied. Our calculations reveal that a 24-atom boron cluster does form closed three-dimensional structures. All isomers show a staggered arrangement of nearest-neighbor atoms. Such a staggering facilitates sp² hybridization in boron clusters. A polarization of bonds between the peripheral atoms in the ring and planar isomers is also seen. Finally, we discuss the fusion of two boron icosahedra. We find that the fusion occurs when the distance between the two icosahedra is less than a critical distance of about 6.5 a.u.