Density functional theory study of BnC (n = 1-7) clusters

The geometrical structures and relative stabilities of boron-rich boron carbon clusters BnC (n = 1-7) are investigated using density functional theory calculations. The planar multi-cyclic geometries for n = 3-7 with C atom at the apex with most B-C bonds and most three-coordination boron atoms are the most stable structures. It is interesting that the C atoms reside in the apexes not doped in the B rings, that is the doped C atoms prefer to the surface of the B structures and do not change the frame structures of B clusters. The compact 3D structures and the linear isomers, however, are energetically more unfavorable for n = 3-7 with the increase of the size. The calculated disproportionation energy, binding energy and HOMO-LUMO gaps show that the B2C and B6C clusters are magic clusters.