Edge states and possible magnetic states in nanographene and open-shell conjugated systems

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 finite onsite Coulomb repulsions. When the number of defects is odd, magnetic solutions are obtained only. The spin density reflects the symmetry of the molecules. We also consider possible magnetic states in buckybowl molecules. We find localized spin order in the sumanene molecule and a part of the C60