title: The mechanism of single-walled carbon nanotube growth and chirality selection induced by carbon atom and dimer addition.
abstract: On the basis of abounding density function calculations, a mechanism is proposed to explain single-walled carbon nanotube (SWCNT) growth and chirality selection induced by single C atom and C(2) dimer addition under catalyst-free conditions. Two competitive reaction paths, chirality change induced by single C atom and nanotube growth through C(2) dimer addition, are identified. The structures of the intermediates and transition states along the potential energy surfaces during the formation of near-armchair (6,5), (7,5), (8,5), and (9,5) caps initiated from the armchair carbon cap (5,5) are elucidated in detail. The results show that the direct adsorptions of C atom or C(2) dimer on growing carbon caps have no energy barrier. Moreover, the incorporations of adsorbed C atom or C(2) dimer display low energy barriers, indicating SWCNT growth and chirality change are thermodynamically and kinetically feasible under catalyst-free growth conditions. In addition, the results also highlight that the concentrations of C atoms and C(2) dimers in the experimental environment would play a critical role in the chiral-selective SWCNT synthesis. Potential opportunities exist in achieving the (n,m) selective growth by delivering single C atom or C(2) dimers at different ratios during different reaction stages.
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459, Singapore.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Man-Fai
authors.initials: MF
authors.lastname: Ng
authors.forename: Shuo-Wang
authors.initials: SW
authors.lastname: Yang
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Yang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
mesh_terms: D019281:Dimerization; D005240:Feasibility Studies; D008958:Models, Molecular; D008968:Molecular Conformation; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D037742:Nanotubes, Carbon