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lab:research:cnt
Table of Contents
Carbon Nanotubes
Using ab initio density functional theory and semi-empirical theories, we have studied various properties and applications of carbon nanotubes (CNTs), which are seamless cylinders wrapped from graphene.
Equilibrium and electronic structures of singlewall CNTs
There are variety of different computational results on the same CNTs
with the same computational method. To resolve this issue, we swapped
completely the configurational spaces of each CNT considering its
structural symmetry determined by either as well as achiral (armchair
and zigzag) and chiral CNTs. As a result, We were able to identify the
most stable structure and the coupling effects between structural and
electronic properties.
Orientational melting in CNT ropes
Using Monte Carlo simulations, we have investigated the possibility of an orientational melting transition within a “rope” of CNTs. hen twisting nanotubes bundle up during the synthesis, orientational dislocations or twistons arise from the competition between the anisotropic interbute interactions, which tend to align neighboring tubes, and the torsion rigidity that tends to keep individual tubes straight. We mapped the energetics of a rope containing twistons onto a alttice gas model and found that the onset of a free “diffusion” of twistons, conrresponding to orientational melting, occurs at TOM ≥ 160 K.
- Orientational Melting in Carbon Nanotube Ropes
Young-Kyun Kwon and David Tomanek, Phys. Rev. Lett. 84 (7), 1483-1486 (2000).
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Effect of intertube interaction in CNTs
We explored the effect of intertube interaction in bundles of single-wall CNTs and multiwall CNTs. Because of small intertube interaction and lattice frustration, we predicted very soft libration modes to occur and to disappear above the orientational melting temperature which marks the onset of free tube rotations about their axis. We also predicted such weak intertube coupling causes an additional electronic band dispersion of < 0.2 eV and opens up a pseudogap of the same magnitude at the Fermi level in the rope of (10,10) SWCNTs. In a (5,5)@(10,10) double wall CNT, the weak interwall interaction and the symmetry reduction causes four pseudogaps to open and close periodically near the Fermi level during the soft librational motaion. This electron-libration coupling, absent in solids composed of fullerenes and SWCNTs, may yield superconductivity in MWCNTs.
- Do Carbon Nanotubes Spin when Bundled ?
Young-Kyun Kwon, David Tomanek, Young Hee Lee, Kee Hag Lee, and Susumu Saito, J. Mater. Res. 13 (9), 2363-2367 (1998).
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- Effect of inter-tube coupling on the electronic structure of carbon nanotube ropes
Young-Kyun Kwon, Susumu Saito, and David Tomanek, Phys. Rev. B 58 (20), R13314-R13317 (1998).
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- Electronic and Structural Properties of Multi-Wall Carbon Nanotubes
Young-Kyun Kwon, and David Tomanek, Phys. Rev. B 58 (24), R16001-R16004 (1998).
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Microscopic growth mechansim of multi-wall CNTs
We investigated the morphology and structural stability at the growing edge of multi-wall CNTs using ab initio and parametrized calculations. We found that the open-ended structures are stabilized against dome closure by strong covalent bonds connecting the exposed edgs of adjacent walls. Growth at the open edge involves rearrangement of these bonds, which are mediated by carbon atoms bridging the gap and change the tip morphology significantly. Presence of a strong ``lip-lip'' interaction can explain formation of carbon nanotubes under annealing conditions.
- Morphology and Stability of Growing Multi-Wall Carbon Nanotubes
Young-Kyun Kwon, Young Hee Lee, Seong-Gon Kim, Philippe Jumd, David Tomanek, and Richard E. Smalley, Phys. Rev. Lett. 79 (11), 2065-2068 (1997).
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lab/research/cnt.txt · Last modified: 2014/12/31 15:19 by ykkwon
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