School of Engineering, University of Borås, SE 501-90 Borås, Sweden.
J Chem Phys. 2013 Aug 7;139(5):054308. doi: 10.1063/1.4816719.
Semiempirical tight binding (TB) and density functional theory (DFT) methods have been used to study the mechanism of single walled carbon nanotube (SWNT) growth. The results are compared with similar calculations on graphene. Both TB and DFT geometry optimized structures of relevance to SWNT growth show that the minimum energy growth mechanism is via the formation of hexagons at the SWNT end. This is similar to the result for graphene where growth occurs via the formation of hexagons at the edge of the graphene flake. However, due to the SWNT curvature, defects such as pentagons are more stable in SWNTs than in graphene. Monte Carlo simulations based on the TB energies show that SWNTs close under conditions that are proper for growth of large defect-free graphene flakes, and that a particle such as a Ni cluster is required to maintain an open SWNT end under these conditions. The calculations also show that the proper combination of growth parameters such as temperature and chemical potential are required to prevent detachment of the SWNTs from the Ni cluster or encapsulation of the cluster by the feedstock carbon atoms.
半经验紧束缚（TB）和密度泛函理论（DFT）方法已被用于研究单壁碳纳米管（SWNT）生长的机制。结果与类似的石墨烯计算进行了比较。TB 和 DFT 几何优化结构与 SWNT 生长有关，表明最低能量生长机制是通过在 SWNT 端形成六边形来实现的。这与石墨烯的结果相似，其中通过在石墨烯薄片的边缘形成六边形来实现生长。然而，由于 SWNT 的曲率，在 SWNTs 中，诸如五边形的缺陷比在石墨烯中更稳定。基于 TB 能量的蒙特卡罗模拟表明，SWNTs 在适当的条件下可以闭合，以便生长大的无缺陷石墨烯薄片，并且需要 Ni 团簇等颗粒在这些条件下保持 SWNT 端的开放。计算还表明，需要适当的生长参数组合，如温度和化学势，以防止 SWNTs 从 Ni 团簇上脱离或团簇被原料碳原子包裹。
