First-principles study of crystalline bundles of single-walled boron nanotubes with small diameter

First-principles calculations based on density functional theory are performed to study structural and electronic properties of crystalline bundles of (n, 0) zigzag and (0, n) armchair-type single-walled boron nanotubes (SWBNT) with small diameter, about 4-6 A. The results predict a modification in the properties of SWBNT bundles relative to those of isolated nanotubes with small diameter. The predicted modification can be attributed to a significant interplay between intra- and inter-tubular bonds in determining the stability of bundles of small diameter SWBNT, analogous to the role played by intra- and inter-icosahedral bonds in the boron crystalline solids.