An ab initio investigation of boron nanotube in ringlike cluster form

Four types of boron nanotubes (BNTs) in the form of double-ring basic units are theoretically predicted. The structure, stability, and electronic properties of these stable BNTs are investigated by the first-principles calculations. The BNT formed by the basic unit with one hole every six atoms on each ring is found to be more stable than those with other three types of basic units. By increasing diameter for boron ring, the stability is enhanced. The density of state demonstrates that BNTs formed by these basic units are metallic.