title: Growth of carbon nanotubes on metal nanoparticles: a microscopic mechanism from ab initio molecular dynamics simulations.
abstract: We report on ab initio molecular dynamics simulations of the early stages of single-walled carbon nanotube (SWCNT) growth on metal nanoparticles. Our results show that a sp2 bonded cap is formed on an iron catalyst, following the diffusion of C atoms from hydrocarbon precursors on the nanoparticle surface. The weak adhesion between the cap and iron enables the graphene sheet to "float" on the curved surface, as additional C atoms covalently bonded to the catalyst "hold" the tube walls. Hence the SWCNT grows capped. At the nanoscale, we did not observe any tendency of C atoms to penetrate inside the catalyst, consistent with total energy calculations showing that alloying of Fe and C is very unlikely for 1 nm particles. Root growth was observed on Fe but not on Au, consistent with experiment.
authors.affiliation: Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550, USA.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Raty
authors.forename: François
authors.initials: F
authors.lastname: Gygi
authors.forename: Giulia
authors.initials: G
authors.lastname: Galli