Initial stage of growth of single-walled carbon nanotubes : modelling and simulations

TL;DR

This study models the initial growth stages of single-walled carbon nanotubes using simulations that incorporate interactions, collisions, and catalytic effects, revealing conditions that favor the formation of precursor structures.

Contribution

It introduces a semi-empirical Hamiltonian combined with a jellium model to simulate carbon-catalyst interactions during SWCNT nucleation, providing new insights into initial growth mechanisms.

Findings

Open cage structures form at optimal charge transfer levels.

Simulations show precursor structures can be achieved in specific conditions.

Implications for nucleation influenced by boundary conditions.

Abstract

Through a careful modeling of interactions, collisions, and the catalytic behavior, one can obtain important information about the initial stage of growth of single-wall carbon nanotubes (SWCNTs), where a state-of-the-art semi-empirical Hamiltonian [Phys. Rev. B, 74, 155408 (2006)] is used to model the interaction between carbon atoms. The metal catalyst forming a supersaturated metal-alloy droplet is represented by a jellium, and the effect of collisions between the carbon atoms and the catalyst is captured by charge transfers between the jellium and the carbon. Starting from carbon clusters in different initial configurations (e.g., random structures, cage structures, bulk-cut spherical clusters, etc.), we anneal them to different temperatures. These simulations are performed with clusters placed in the jellium as well as in vacuum. We find that, in the presence of jellium, and for an optimal charge transfer of ~ 0.1 e-0.2 e, open cage structures (and some elongated cage structures) are formed, which may be viewed as precursors to the growth of SWCNTs. We will also discuss the implications of a spherical boundary on the nucleation of a SWCNT.