First-principles study of optical spectra of single-wall $\mathrm{B}{\mathrm{C}}_2\mathrm{N}$ nanotubes

First-principles calculations based on the density functional theory and the generalized gradient approximation were carried out to systematically investigate the optical properties of $\mathrm{B}{\mathrm{C}}_2\mathrm{N}$ nanotubes. Two types of zigzag nanotubes and two types of armchair nanotubes were considered. It was found that the optical properties of $\mathrm{B}{\mathrm{C}}_2\mathrm{N}$ nanotubes are closely related to their charility and diameter. Depending on the type of the nanotube, redshifts or blueshifts in the absorption peaks were observed which are due to the competition of the size effect and $\pi$ orbital overlapping. Optical anisotropy with different light polarizations was also observed in the absorption spectra and loss function. The peaks in the loss function are attributed to the collective excitations of $\pi$ electrons and the high-frequency $\pi +\sigma$ plasmon.

Figure 1

(Color online) Atomic configuration of an isolated $\mathrm{B}{\mathrm{C}}_2\mathrm{N}$ sheet. Primitive and translational vectors are indicated.

Figure 2

Absorption spectra of AC-1 $(n,n)$: (a) for parallel light polarization and (b) for perpendicular light polarization. The curves are displaced vertically for clarity (also applies to other figures).

Figure 3

Absorption spectra of AC-2 $(m,m)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 4

Absorption spectra of ZZ-1 $(n,0)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 5

Absorption spectra of ZZ-2 $(0,n)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 6

Loss functions of AC-1 $(n,n)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 7

Loss functions of AC-2 $(m,m)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 8

Loss functions of ZZ-1 $(n,0)$: (a) for parallel light polarization and (b) for perpendicular light polarization.

Figure 9

Loss functions of ZZ-2 $(0,n)$: (a) for parallel light polarization and (b) for perpendicular light polarization.