Formation and atomic structure of boron nitride nanotubes with a cup-stacked structure

Boron nitride (BN) nanotubes were synthesized by annealing Fe₄N/B powder at 1000 ^{{ring operator}}C for 1 h in a nitrogen gas atmosphere, and large amounts of BN nanotubes with a cup-stacked structure were obtained after a purification process. The atomic structures of the cup-stacked BN nanotubes were investigated by high-resolution electron microscopy as well as molecular mechanics calculations, and compared with double walled BN nanotubes. The present results indicate that the cup-stacked structure with a cone angle of 20^{{ring operator}} is more stable than the structure with an angle of 38^{{ring operator}} and ordinary nanotube structures.