TY - JOUR
T1 - Quantum Chemical Molecular Dynamics Model Study of Fullerene Formation from Open-Ended Carbon Nanotubes
AU - Zheng, Guishan
AU - Irle, Stephan
AU - Elstner, Marcus
AU - Morokuma, Keiji
PY - 2004/4/15
Y1 - 2004/4/15
N2 - We present quantum chemical molecular dynamics (MD) simulations for a model formation process of fullerene molecules. Trajectories of up to 24-ps lengths were computed for (5,5), (7,3), (8,0), (9,0), (10,0), and (10,5) open-ended single-walled carbon nanotubes for a temperature range between 2000 and 4000 K at various tube lengths, using density functional based tight-binding (DFTB) molecular dynamics. DFTB was selected because geometries and energies obtained are found to qualitatively agree with B3LYP/6-31G(d) results at much smaller cost of computer time. Extremely fast cage formation was observed with simulation times as short as 3 ps, and most simulations at 3000 and 4000 K led to the formation of fullerene structures within less than 14-ps simulation times. Key structural features for the transformation of tubes to fullerenes are identified, such as the overwhelming presence of acetylenic "wobbling C 2 units", which form spontaneously in great abundance at the open ends of the tubes. A comparison of DFTB simulations is made with corresponding semiclassical reactive bond-order force field MD trajectory calculations, which exhibit much slower structural transformations without the "wobbling" C 2 units. We also compare DFTB energetics of optimized MD snapshot structures with B3LYP energies.
AB - We present quantum chemical molecular dynamics (MD) simulations for a model formation process of fullerene molecules. Trajectories of up to 24-ps lengths were computed for (5,5), (7,3), (8,0), (9,0), (10,0), and (10,5) open-ended single-walled carbon nanotubes for a temperature range between 2000 and 4000 K at various tube lengths, using density functional based tight-binding (DFTB) molecular dynamics. DFTB was selected because geometries and energies obtained are found to qualitatively agree with B3LYP/6-31G(d) results at much smaller cost of computer time. Extremely fast cage formation was observed with simulation times as short as 3 ps, and most simulations at 3000 and 4000 K led to the formation of fullerene structures within less than 14-ps simulation times. Key structural features for the transformation of tubes to fullerenes are identified, such as the overwhelming presence of acetylenic "wobbling C 2 units", which form spontaneously in great abundance at the open ends of the tubes. A comparison of DFTB simulations is made with corresponding semiclassical reactive bond-order force field MD trajectory calculations, which exhibit much slower structural transformations without the "wobbling" C 2 units. We also compare DFTB energetics of optimized MD snapshot structures with B3LYP energies.
UR - http://www.scopus.com/inward/record.url?scp=2342626530&partnerID=8YFLogxK
U2 - 10.1021/jp0373090
DO - 10.1021/jp0373090
M3 - Article
AN - SCOPUS:2342626530
SN - 1089-5639
VL - 108
SP - 3182
EP - 3194
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 15
ER -