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 (PBEGGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The results show a semiconducting nature with direct and indirect gap for […]