Effect of Metal Cluster-Cap Interactions on the Catalyzed Growth of Single-Wall Carbon Nanotubes

Abstract

Density functional theory is employed to investigate the interactions between a nine-atom cobalt cluster and single-wall carbon nanotube caps with chiral angles ranging from near zigzag to armchair. With the aim of analyzing the initial stages of nanotube growth, the caps used in our study are the minimal units for which chirality can be defined. Electrostatic potential maps, atomic charges, and electronic density of states are analyzed for the individual caps and cluster and for the cap/cluster coupled system to detect changes triggered by the cap/cluster interactions. It is observed that the metal cluster becomes oxidized, and significant changes are detected in its geometry; such changes are dependent on the cap chirality. Strong electrostatic interactions are found between the cap rim atoms and the cobalt atoms in contact with them. However, the bonding orbitals involved in such strong interactions are dominated by inner rather than by frontier orbitals, which are the ones that most likely would be able to participate in nanotube growth reactions. Among other findings, our results suggest that armchair and near-armchair systems should be the most favored when the growth mechanism is dominated by reactions such as C 2 addition to the cap rim atoms.

Carbon Nanotube Mass Production: Principles and Processes

“…[172] Strong electrostatic interactions, which are dominated by inner rather than frontier orbitals, are found between the cap rim atoms and the metal atoms they are in contact with. [173] To know the atom-by-atom growth of SWCNTs, in situ atomic characterization of CNT growth is needed. [159,160,174] Theoretical simulation is also a good way to get the atomic details of the growth of CNTs.…”

“…[178] The armchair and near-armchair CNTs are mostly produced when the growth mechanism is dominated by reactions such as C 2 addition to the cap rim atoms. [173] These ideas on CNT formation will enlighten the strategy for chirality control of manufactured CNTs.…”

Carbon nanotube growth: First-principles-based kinetic Monte Carlo model

“…These calculations include DFT geometry optimization [13][14][15][16], molecular dynamics (MD) [17][18][19][20][21][22][23][24][25], and tight binding Monte Carlo (TBMC) simulations [26][27][28], in which different aspects of the CNT growth process were studied, e.g. role of carbon/catalyst/support interaction [16,19], catalyst nanoparticle state [17,18], or CNT growth with chiralities [29][30][31][32]. Despite these efforts, very little is known about the exact chemistry on the catalyst, especially pertaining to the growth mechanism of CNT.…”

Simulation and modeling of carbon nanotube synthesis: current trends and investigations

“…Gomez-Gualdron and Balbuena [39] employed the density functional theory to investigate the influence of metal cluster-cap interactions on the catalyzed growth of SWCNTs, in simulations to investigate the nucleation on metal catalyst particles. Electrostatic potential maps, atomic charges and electronic density of states were analyzed for the individual caps and cluster, and for the cap/ cluster coupled system, to detect changes triggered by the cap/cluster interactions, as shown in Figure 6C.…”

“…The quantum effect in nanotube growth has been considered in the simulation by Gomez-Gualdron and Balbuena [39] in their ab initio calculations. The methodology utilized DFT with the three-parameter Becke gradient-corrected exchange functional, in conjunction with the Lee-Yang-Parr correlation functional (B3LYP).…”