Effect of Cap-Catalyst Structural Correlation on the Nucleation of Carbon Nanotubes
M Luo and ES Penev and AR Harutyunyan and BI Yakobson, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 18789-18794 (2017).
Helicity of a carbon nanotube is determined by the pentagon distribution in the nucleus-cap. In catalytic growth, the shape of the metal catalyst could possibly affect the pentagon arrangement intuitively, by matching the disclinations-pentagons to the vertices of underlying solid metal. Here we explore this effect by atomistic simulations of all possible nanotube caps of diameter d similar or equal to 0.8 nm on a Ni icosahedron. Although the vertices of the polyhedral particle result in energy differences between various cap configurations, the interface energy of the cap on the metal catalyst is still the dominant thermodynamic factor during nucleation. Further, a dynamic "edge- etching" algorithm reveals that the nucleation barrier can occur before cap completion. Although control of the nucleation barrier positions of different caps may be achieved through the chemical potential of the carbon feedstock, the barrier heights are found to be comparable for all caps, suggesting limited ability for chiral selectivity.
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