First-principles calculations on the open end of single-walled AlN nanotubes

Using density functional theory with the generalized gradient approximation, we have studied geometrical and electronic structures of open-ended armchair and zigzag single-walled Aluminum nitride (AlN) nanotubes. For small armchair AlN nanotubes, at least with the diameter less than that of the (8,8) nanotube, a self-closure behavior occurs due to the interaction between dangling bonds of Al and N atoms at the open end. Especially for the (4,4) AlN nanotube, a hemispherical cap with an octagon is formed, which is one half of a round Al24N24 nanocage. The ionization potential of the Al-terminated zigzag AlN nanotube is smaller than that of the N-terminated one.