Microscopic Growth Mechanisms for Carbon Nanotubes
Jean-Christophe Charlier,
*
Alessandro De Vita,
Xavier Blase,
Roberto Car
The uncatalyzed edge growth of carbon nanotubes was investigated by
first-principles molecular dynamics simulations. At experimental temperatures the open end of single-walled nanotubes closed
spontaneously into a graphitic dome, which may explain why these
nanotubes do not grow in the absence of transition metal catalysts. On
the other hand, chemical bonding between the edges of adjacent coaxial tubes ("lip-lip" interactions) trapped the end of a double-walled nanotube in a metastable energy minimum, thus preventing dome closure.
These calculations show that this end geometry exhibits a high degree
of chemical activity and easily accommodates incoming carbon fragments,
supporting a model of growth by chemisorption from the vapor phase.
Institut Romand de Recherche Numérique en
Physique des Matériaux, Ecublens, CH-1015 Lausanne, Switzerland.
*
Permanent address: Unité de Physico-Chimie et de
Physique des Matériaux, Université Catholique de Louvain,
Place Croix du Sud 1, B-1348 Louvain-la-Neuve, Belgium.
Permanent address: Département de Physique des
Matériaux (UA 172), Université Claude Bernard, 43 bd. du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France.
To whom correspondence should be addressed.
