Quantum-chemical semi-empirical molecular-orbital calculations of zigzag graphene nanoribbons (nzGNRs) were done for the number of zigzag carbon chains n=4 and 10. The antiferromagnetic (AFM) nature of zGNRs' ground state was confirmed. The energy difference between AFM and ferromagnetic (FM) states was calculated, and dimerization patterns of their chemical bond lengths were elucidated. The electron energy band structure calculations show that narrow nanoribbon (4 zGNR) is semiconducting in both AFM and FM states. For wider nanoribbon (10 zGNR), the AFM state is semiconducting (≈0.1 eV band gap), whereas the FM state is half-metallic (electrical conduction with only one spin orientation).
Structural and energy characteristics of the smallest magnetic endofullerene Fe@C20 have been calculated using the density functional theory approach. The ground state of Fe@C20 is found to be a septet state, and the magnetic moment of Fe@C20 is estimated to be 8 Bohr magnetons. Characteristics of an (8,8) carbon nanotube with a single Fe@C20 inside are studied in the framework of the semiempirical approach. The scheme of a magnetic nanorelay based on cantilevered nanotubes filled with magnetic endofullerenes is elaborated. The proposed nanorelay is turned on as a result of bending of nanotubes by a magnetic force. Operational characteristics of such a nanorelay based on (8,8) and (21,21) nanotubes fully filled with Fe@C20 are estimated and compared to the ones of a nanorelay made of a (21,21) nanotube fully filled with experimentally observed (Ho3N)@C80 with the magnetic moment of 21 Bohr magnetons. Room temperature operation of (21,21) nanotube based nanorelays is shown.
We have carried out semiempirical molecular orbital calculations of C Z+/60 cations and their elongated isomers-C20+40 barrelenes. The highest possible metastable charge state of a fullerene ion was found to be C 14+/60. For this charge state the lowest energy isomer is not a spherical buckyball, but an elongated barrelene. For Z≥8, the fission channels C Z+/20+40 - C (Z-2)+/20+20 + C 2+/20 are open, the energy difference between fullerene and barrelene isomers being less than 10 eV. We have calculated the energy releases in this type of fission reactions for positive charge states of barrelenes Z=8,10,12,14 and dissociation energy thresholds for Z=4,6. The reaction coordinate calculations of C 6+/20+40 - C 4+/20+20 + C 2+/20 fission and estimate of fission Coulomb barrier have been done.