Energetics and Electronic Structures of EncapsulatedC60in a Carbon Nanotube

Abstract

We report total-energy electronic structure calculations that provide energetics of encapsulation of C60 in the carbon nanotube and electronic structures of the resulting carbon peapods. We find that the encapsulating process is exothermic for the (10,10) nanotube, whereas the processes are endothermic for the (8,8) and (9,9) nanotubes, indicative that the minimum radius of the nanotube for the encapsulation is 6.4 A. We also find that the C(60)@(10,10) is a metal with multicarriers each of which distributes either along the nanotube or on the C60 chain. This unusual feature is due to the nearly free electron state that is inherent to hierarchical solids with sufficient space inside.

Energetics of carbon peapods: Elliptical deformation of nanotubes and aggregation of encapsulatedC60

“…24,25 The valence wave functions are expanded by the plane-wave basis set with a cutoff energy of 50 Ry ͑680.25 eV͒, which gives enough convergence of the relative total energies of carbon-related materials. 13 We have adopted a supercell model in which a nanotube is placed with its wall positioned 6 Å away from the outer wall of an adjacent nanotube. Along the tube direction, we have imposed a commensurability condition between the onedimensional periodicity of the atomic arrangements in the nanotube and that of the chain of C 60 .…”

“…The t 1u states are partially occupied by electrons transferred from the nanotube, and the C 60 are weakly bound to each other by a weak intermolecular interaction. 13 These facts are expected to induce the modulation of the alignment of C 60 in the nanotubes. However, such modulation with double periodicity does not take place in the system.…”

“…In this hierarchical solid, the electronic structure is found to depend on the electronic structure of each constituent and on the space between them. [13][14][15] For instance, the fundamental energy gap of peapods consisting of semiconducting nanotubes changes in a range from moderate gap semiconductors to metals by varying the type of encapsulated fullerene species. 15 In our previous researches, it was also found that the space between encapsulated fullerenes and nanotubes plays a crucial role in determining their energetics.…”

Modeling spin interactions in carbon peapods using a hybrid density functional theory

“…Density functional theory ͑DFT͒ calculations have been reported on several model systems, such as SWNTs containing C 60 , K x C 60 , Y@C 60 , C 82 , La@C 82 , La 2 @C 82 , and Sc 3 N@C 80 . [10][11][12][13][14][15][16][17] To date little work has been done on understanding the spin properties of peapods and the above mentioned issues ͑ii͒, ͑iii͒, and ͑iv͒ have not been addressed in detail thus far. We have computed the charge and spin distributions and the electronic structures within Sc@ C 82 chains and peapod structures.…”

Quantum-information-processing architecture with endohedral fullerenes in a carbon nanotube

“…The electronic spins of neighboring molecules interact by dipole-dipole couplings. In this scheme, we have neglected the C60-SWCNT interaction [14,15], which are far from the resonance frequency of the electron spin under our consideration. Experimentally, the C60-SWCNT interaction is not sufficiently large to account for the observed scanning tunneling spectroscopy (STS) images [15].…”