期刊
ACS NANO
卷 3, 期 11, 页码 3413-3420出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn900784f
关键词
quantum chemical molecular dynamics simulations; density functional tight binding; self-assembly; continued carbon nanotube growth; iron catalyst nanoparticle; nonequilibrium dynamics
类别
资金
- CREST (Core Research for Evolutional Science and Technology)
- Japan Science and Technology Agency (JST)
- Special Coordination Funds for Promoting Science and Technology (SCF)
- Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan
The atomic scale details of single-walled carbon nanotube (SWNT) nucleation on metal catalyst particles are elusive to experimental observations. Computer simulation of metal-catalyzed SWNT nucleation is a challenging topic but potentially of great importance to understand the factors affecting SWNT diameters, chirality, and growth efficiency. In this work, we use nonequilibrium density functional tight-binding molecular dynamics simulations and report nucleation of sp(2)-carbon cap structures on an iron particle consisting of 38 atoms. One C-2 molecule was placed every 1.0 ps around an Fe-38 cluster for 30 ps, after which a further 410 ps of annealing simulation without carbon supply was performed. We find that sp2-carbon network nucleation and annealing processes occur in three sequential and repetitive stages: (A) polyyne chains on the metal surface react with each other to evolve into a Y-shaped polyyne junction, which preferentially form a five-membered ring as a nucleus; (8) polyyne chains on the first five-membered ring form an additional fused five- or six-membered ring; and (C) pentagon-to-hexagon self-healing rearrangement takes place with the help of short-lived polyyne chains, stabilized by the mobile metal atoms. The observed nucleation process resembles the formation of a fullerene cage. However, the metal particle plays a key role in differentiating the nucleation process from fullerene cage formation, most importantly by keeping the growing cap structure from closing into a fullerene cage and by keeping the carbon edge alive for the addition of new carbon material.
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