Electronic structures and work functions of BC3 nanotubes: A first-principle study

摘要

The electronic structures and work functions of the single-wall BC3 nanotubes are studied by the first-principle method. In contrast to the armchair nanotubes, the zigzag nanotubes are indirect-band semiconductors. The zigzag nanotubes can be further classified into two types, depending on the wave-vector characteristics of the conduction band minima. The bandgap energies of the armchair nanotubes are always smaller than that of the BC3 sheet, and increase with the nanotube diameter. For the two types of zigzag nanotubes, the bandgap energies are always larger than that of the BC3 sheet, and decrease with the nanotube diameters. Analysis of the bond angles between the neighboring atoms on the nanotube walls shows that the mixing of the n and a electron orbitals exhibits opposite trends for the armchair and zigzag nanotubes. These trends are not only responsible for the above dependence of the electronic structures on the types and diameters of the nanotubes, but also give physical insight to the indirectness of the band-structures of the zigzag nanotubes. By the first-principle method, it is found that the work functions of both armchair and zigzag nanotubes scale linearly with 1/D~2, D being the nanotube diameter. Moreover, it is found that the per-atom strain energies and the vacuum bandwidths of both armchair and zigzag nanotubes satisfy universal relations which also scale linearly in 1/D~2.