We calculate the magnetic moment caused by the persistent currents in polygonal carbon nanotube tori by the tight binding model. The polygonal CNT tori are formed by introducing heptagonal and pentagonal defects along the inner hole and outer fringe, respectively. We found a new type of large paramagnetic persistent current caused by the semi-metallic band structures of the

In a telescoped double-walled nanotube with the inner tube partially extracted from the outer tube, the total current is forced to flow between the layers. Considering the interlayer Hamiltonian as a perturbation, we can obtain an analytic formula for the interlayer conductance. The accuracy of the perturbation formula is systematically improved by including higher order terms. The interlayer interaction effective in the perturbation formula is the product of the interlayer Hamiltonian and the wave function. It clarifies the effects of the spatial range of the interlayer Hamiltonian and the band energy shift.

We demonstrate the ability of our cluster expansion approach (CEA) for cohesive energies of alloys, which allows one to study the chemical trends of the relative stability of different atomic structures of alloys, as an example, X dependence of the atomic structures of Al-rich AlX (X = Sc-Zn) alloys, including ordered structures (L1 2 (Al 3 Sc), DO 22 (Al 3 V)), a Mackay icosahedron (a local structure in the Al 80 Mn 20 quasicrystal), and precipitate shapes in decomposition phases (Al 1Àc Cu c , Al 1Àc Zn c ; c < 0:05). All the terms in the CEA for Al-rich AlX alloy can be determined uniquely and successively from low-order to high-order by using the total energies of isolated Al and X atoms, pure Al and X metals, and X impurities in Al metal. The total energies of impurity systems are calculated accurately by using the all-electron full-potential Korringa-Kohn-Rostoker (FPKKR) Green's function method, combined with the density-functional theory in the generalized-gradient approximation (GGA). We show: (1) the binding energies of X (X = Cu, Zn) impurities in Al are reproduced very well by the CEA including two-and three-body interaction energies of X impurities; (2) the chemical trends of structural stability among ordered structures (L1 2 , DO 22 , DO 23 ) of Al 3 X (X = Sc, Ti, V), being determined by use of the screened-FPKKR and GGA band-structure calculations, are reproduced by the CEA including only two-body (X-X) interaction energies in Al.

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The conditions necessary for a nanotube junction connecting a metallic and semiconducting nanotube to rectify the current are theoretically investigated. A tight binding model is used for the analysis, which includes the Hartree-Fock approximation and the Green's function method. It is found that the junction has a behavior similar to the backward diode if the gate electrode is located nearby and the Fermi level of the semiconducting tube is near the gap. Such a junction would be advantageous since the required length for the rectification could be reduced.Comment: 4 pages, RevTeX, uses epsf.st