Ab initio study on the structural, energetic and electronic features of the asymmetric armchair SWCNT junctions

The structural, energetic and electronic features of asymmetric armchair single-walled carbon nanotube (SWCNT) junctions have been studied by ab initio calculations at the B3LYP/6-31G∗//HF/3-21G∗ levels. The junctions are composed of two SWCNTs with different radius, which are connected by a set of 5-membered and 7-membered carbon rings. The results show that the metallic-metallic junction is more energetically favorable if the junction is formed with a hexagon inserted between the pentagon-heptagon (5/7) pair defects in the armchair nanotube. The shift of the spatial distribution of HOMO and LUMO shows that the asymmetric electronic structure of the junction could be used as a molecular rectifier.