Electronic and Optical Properties of Low-Dimensional B₂CN Nanomaterials from First Principles

The structures and electronic and optical properties of B 2 CN sheet and single-walled B 2 CN nanotubes were investigated by the first-principles density functional calculations. By rolling up the planar low-energy B 2 CN nanosheets along various chiral vectors, four types of zigzag and armchair B 2 CN nanotubes were constructed. The present calculations show that the structural and electronic properties of B-rich B 2 CN nanotubes strongly depend on their sizes and chiralities. The zigzag and armchair B 2 CN nanotubes with the small diameter generally are semiconductors, and their band gaps decrease as the tube-radius increases. When the diameter of tubes is large enough, the four kinds of nanotubes may produce the electronic behavior transitions from semiconductor to metal. Owing to the electronic affinity difference among B, C, and N atoms, there are remarkable charge transfers from B to C and N atoms in B 2 CN nanostructures. The predicted dielectric and optical properties show that the zigzag and armchair B 2 CN nanotubes are the optical anisotropy with respect to light polarization, and their absorption spectra are sensitive to the chirality of tube.