Structural and electronic properties of 240° nanocones

An original nanocone with 240degrees disclination arises naturally from a planar hexagonal sheet when four 60degrees segments originating from adjacent hexagonal centers are cut out of the plane and the severed edges of the segments are rejoined. The comparison among the calculated total energies of several pure carbon nanocones with this same 240degrees disclination but built from different growth modes shows that the cone with four 60degrees segments is the most stable one. The geometric structures are optimized and the density-functional theory is employed to perform total energy calculations. Defined the designability and the stability of this carbon structure, with four pentagons sharing two atoms at the apex, we simulate a similar BN nanocone by clusters containing 58 B plus N atoms and additional 12 H atoms to saturate the dangling bonds at the edge. Depending on the choice of the sharing atoms (BN, BB, or NN), the local densities of states near the apexes are investigated and sharp resonant states are found to dominate the electronic structure in the region close to the Fermi energy.