Theoretical study of defects of BN nanotubes: A molecular-mechanics study

We investigate the structure and the formation energy of the pentagon-heptagon pairs (5775) defects of BN nanotubes using a molecular-mechanics method. For (n, 0) BN nanotubes, the homoelemental bonds of the 5775 defect may be located nearly either parallel or perpendicularly in the direction of tube axis. The former is energetically favored and strongly affects the reduction of the strain with decreasing radius. The formation energy of the 5775 defect, which increases with increasing radius, is lower than that of the tetragon-octagon pairs (4884). The 5775 defect of BN nanotubes is structurally and energetically stable, as compared to the 4884 defect.