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| Kikuo Harigaya. |
| Nano-carbon materials are investigated intensively. In this paper, the edge-state in nanographene materials with zigzag edges is studied theoretically. In particular, while the inter-layer interactions are considered, we prove that edge states exist at the energy of the Dirac point in the doubly stacked nanographene, and in the case of the infinitely-wide lower layer case. This property applies both for the A-B and A-C stackings. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3878/version/1 |
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| Kikuo Harigaya. |
| Nanocarbon materials are investigated intensively. In this paper, the edge-state in nanographene materials with zigzag edges is studied theoretically. In particular, while the inter-layer interactions are considered, we prove that edge states exist at the energy of the Dirac point in the doubly stacked nanographene, and in the case of the infinitely-wide lower layer case. This property applies both for the A-B and A-C stackings. We also study possible magnetic properties in fullerenes with defects and buckybowl molecules. When the number of lattice defects in C60 is even, we obtain magnetic and nonmagnetic solutions. The total energy of the nonmagnetic solution is lower than that of the magnetic solution. The occurrence of the localized spin is reduced for... |
| Tipo: Presentation |
Palavras-chave: Chemistry. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3880/version/1 |
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| Kikuo Harigaya. |
| 1. Topological materials: Moebius nanographite and conjugated polymers
2. Magnetic domain wall states [1] vs. helical magmetic order in nanographite [2]
3. Static polarizability [alpha] and the first hyperpolarizability [beta] are studied, comparing three models: Mobius strip cyclacene, ring cyclacene, and linear strip.
4. Opening the knot of the Mobius to form the ring leads to the increase of [alpha] from 268 to 323 a.u. and [beta] increases about three times from 393 to 1049 a.u.
5. Opening the ring to form the linear strip, [alpha] increases from 323 to 476 a.u. [beta] as well increases about three times from 1049 to 2814 a.u.

[1] K. Wakabayashi and... |
| Tipo: Presentation |
Palavras-chave: Chemistry. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3881/version/1 |
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| Kikuo Harigaya. |
| Exciton effects are studied in single-wall boron-nitride (BN) nanotubes. Linear absorption spectra are calculated with changing
the chiral index of the zigzag nanotubes. We consider the extended Hubbard model with atomic energies at the boron and nitrogen sites.
Exciton effects are calculated using the configuration interaction technique. The Coulomb interaction dependence of the band gap,
the lowest exciton energy, and the binding energy of the exciton are discussed. The optical gap of the (5,0) nanotube is about 6 eV
at the onsite interaction U=2t with the hopping integral t=1.1 eV. The binding energy of the exciton is 0.50 eV for these parameters.
This energy agrees... |
| Tipo: Presentation |
Palavras-chave: Chemistry. |
| Ano: 2009 |
URL: http://precedings.nature.com/documents/3879/version/1 |
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