Abstract Submitted to the NANOTUBE-99 Workshop:

Results of ab initio and parametrized Linear Combination of Atomic Orbitals (LCAO) calculations indicate that the interaction between adjacent nanotubes gives rise to a non-trivial potential energy surface and intriguing modifications of the electronic structure. In multi-wall nanotubes [1] and "ropes" consisting of single-wall nanotubes [2,3], inter-wall interaction may open up one or several pseudo-gaps close to the Fermi level. This modification of the electronic structure is postulated to play a very important role in electron transport, which we calculate using the Landauer-Büttiker formalism [4].

The electronic structure and dynamics of interacting multi-walled or bundled nanotubes is furthermore modified by the librational motion of the individual tubes. We expect an important contribution to the dynamics and the electronic structure to arise from orientational dislocations or twistons which we postulate to be frozen in during the synthesis, due to the competition between the anisotropic inter-tube interaction and the torsion rigidity of individual tubes. Using a Monte Carlo simulation, we find that the onset of free "diffusion" of twistons, corresponding to orientational melting, occurs at T_OM~100K [5].

We also study the intriguing dynamics of multi-wall nanotubes or nano-capsules containing smaller fullerenes, which can be considered as two-level systems. We show that the C480 nano-capsule, containing a K@C60+ endohedral complex, may find a potential application as a non-volatile memory element that can be switched by applying electric field between the end-caps of the capsule [6]. This is shown in the corresponding molecular dynamics simulation of a nanotube-based memory element.

[1]. Young-Kyun Kwon, and David Tománek, Phys. Rev. B 58, R16001 (1998).
[2]. P. Delaney, H.J. Choi, J. Ihm, S.G. Louie, and M.L. Cohen, Nature, 391, 466 (1998).
[3]. Young-Kyun Kwon, Susumu Saito, and David Tománek, Phys. Rev. B 58, R13314 (1998).
[4]. Stefano Sanvito, Young-Kyun Kwon, David Tománek, and Colin Lambert, in preparation.
[5]. Young-Kyun Kwon, and David Tománek, in preparation.
[6]. Young-Kyun Kwon, David Tománek, and Sumio Iijima, Phys. Rev. Lett. 82, 1470 (1999).

^* Work supported by the Office of Naval Research under Grant No. N00014-99-1-0252.

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