Abstract
Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level.
Highlights
Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism
We report on carbon nanotubes (CNTs) cap nucleation using different hydrocarbon species at different temperatures to unravel the initiation of CNT growth by combined reactive molecular dynamics (MD) and time-stamped force-bias Monte Carlo simulations[37]
We find that the competition betweenhydrogenation and dehydrogenation processes during the incubation stage is critical for the dynamics of the cap formation and subsequent CNT growth process
Summary
Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. We report on atomic scale simulations of cap nucleation of singlewalled carbon nanotubes from hydrocarbon precursors. The role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The first dynamic simulation studies appeared on related processes using hydrocarbon molecules as carbon feedstock[4]. Wang et al.[35] studied the interaction of acetylene with a Fe38 cluster by density-functional tight-binding simulations and concluded that cap formation is not a necessary condition for single-walled CNT (SWNT) nucleation and large hydrocarbon clusters can grow before hydrogen abstraction would allow the formation of a carbon-only tubular structure. We report on CNT cap nucleation using different hydrocarbon species at different temperatures to unravel the initiation of CNT growth by combined reactive MD and time-stamped force-bias Monte Carlo (tfMC) simulations[37]
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