End cap nucleation of carbon nanotubes

An easily applied graphical approach for facilitating precise tailoring during computational construction of model uncapped or capped single-wall nanotubes or fullerenes is delineated and utilized in this paper. The main enabling concepts are the commonly suggested growth mechanisms for single- and multi-walled carbon nanotubes mediated by end cap structures. The construction protocol described herein can be used to rapidly create any type of armchair, zigzag, chiral or nonchiral defect-free nanotube. Any desired, feasible combination of length and diameter, along with specific placement of hexagonal and pentagonal rings or end caps, can also be controlled. A classification system for end caps is also developed in order to help simplify choosing or describing the particular carbon system under investigation. The suggested methodology is used to systematically model heats of formation of a variety of carbon nanotubes and related fullerenes using AM1 semiempirical calculations. The main factors affecting the calculated physical properties, other than size, are the structures of the various base and terminating end caps. Finally, we comment on the possible relationship of the construction methodology to mechanisms for carbon nanotube nucleation.