New type of carbon nanotubes - narrow nanotubes - has recently been observed with diameters of 4-5Å. It has been postulated that the narrow nanotubes are closed by fullerene fragments of C20 and C36. This paper presents computational results on related model nanotubes with stoichiometries such as C80, C84, C96, C108, or C120. The computations were carried out at the PM3, AM1, SAM1, HF/3-21G, HF/4-31G, and B3LYP/6-31G* levels. Two C36 fullerenes were considered, D6h and D2d. At the PM3 level and with the C84 nanotube stoichiometry, the D2d cage closure gave a lower energy (by 185kcal/mol and a diameter of 5.42Å). There is another possible candidate, a C32 cage with D4d symmetry (two four-membered rings). At the PM3 level and with the C96 nanotube stoichiometry, the D4d closure (with a diameter of 5.43Å) had energy lower by 210kcal/mol than that of the D6h nanotube closure. On the other hand, four-membered rings should not play a significant role for narrow nanotubes with a diameter of 4Å, where the dodecahedron-related closure should be exclusive. Still narrower nanotubes are briefly discussed.
- Four-membered rings
- Narrow nanotubes
- Smaller fullerenes
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Computer Graphics and Computer-Aided Design
- Materials Chemistry