DFT investigation of optoelectronic properties of ultra-small C, CN and SiC nanotubes

We investigated the optoelectronic properties of ultra-small armchair (3,3) carbon (C), carbon nitride (CN) and silicon cabride (SiC) nanotubes using the density functional theory (DFT). We performed the calculations for two potentials Perdew-Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The results show a semiconducting nature with direct and indirect gap for C and SiC nanotubes respectivelly and metallic nature for CN nanotube. The calculated refractive index show an anisotropic bahaviour and decreases for all nanotubes and become less than one providing the photoluminescence phenomenon.