Honeycomb lattice structure of graphene, characterized by the two basis vectors and . A nanotube is formed by rolling up the 2D sheet so that the end of the chiral translation vector at [here (6,3)] meets the origin O. The nanotube translation vector is directed along the tube axis. The angle between (the zigzag direction) and is the chiral angle . This figure is used with permission from S. Mirayama.
A single-wall carbon nanotube containing a row of closed carbon shells concentric with the tubule axis. The diameter and center-to-center spacing of the internal shells are consistent with a chain of molecules. The nanotube is surrounded by a vacuum. Scale bar, . From Ref. 32.
Calculated Kohn–Sham orbital energy patterns of . Adapted after Ref. 122. Adapted from Ref. 26, with permission from the American Chemical Society 1996.
The binding energy of a molecule to the inside wall of a single-wall nanotube as a function of tube radius (a). The entrance potential for a molecule near the open end of a (10,10) single-wall nanotube. From Ref. 26 (b).
Simple model of a voltage-biased peapod structure close to a metal electrode. The peapod is a chain of molecules inside a SWNT with an open end. A large enough bias voltage will make it possible to charge the outermost molecule and expel it from the SWNT (see text).
Potential energy difference as a function of buckyball position for an extra electron on the buckyball surface and on the SWNT calculated using the model system shown in Fig. 5. Here has been plotted for the case when the electrode in Fig. 5 is biased at with respect to the grounded nanotube; is the length and is the radius of the SWNT, is the distance between the tube opening and the metal electrode, and is measured from the electrode. An electron is only transferred to the buckyball when , where is the radius of the molecule, becomes equal to the difference between the SWNT work function and the affinity level energy. Here , so the applied bias in this case is not enough to charge the buckyball; for the parameters used a bias voltage of is required (see text). Note that does not go to zero far inside the nanotube. This is because some electrostatic energy can be gained by creating a “hole” in the electron gas on the nanotube surface near a charged buckyball. In agreement with experiment this is, however, not enough to charge a buckyball far inside the SWNT.
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