Theoretical investigation on the cylinder-shaped N₆₆ cage

Recent theoretical studies suggested that the stabilizing factors for large nitrogen cages tend to favor more five-membered rings, more three-membered rings and cylinder-shaped structure with large numbers of layers. Our present studies on the relative stability of all-nitrogen cages suggest that the stabilizing factors originate from the dispersion interactions. The cylinder-shaped of N₆₆ (with D_3h symmetry) has been studied in detail. The structure and energies are examined at the B3LYP/cc-pVDZ level. In addition, single-point energy calculations at the MP2/cc-pVDZ and the B3LYP/cc-pVTZ levels are carried out in order to determine whether or not dispersion interactions exist in N₆₆. To fully understand the bonding in this cage molecule, NBO and AIM analyses are performed. The results show that the dispersion interactions contribute to the stability of the cylinder-shaped N₆₆. Meanwhile, electrostatic potential analysis shows that N₆₆ has negative electrostatic potential on the outside and positive electrostatic potential inside the tube. As the eleventh member of the series (N₆)_n (n=1-30, with D_3h or D_3d symmetry alternatively), cylinder-shaped N₆₆ may also be a novel beeline nanotube which is environmentally friendly. This work is expected to impact a wide range of applications. © 2012 Elsevier B.V.