Theoretical Studies On The Electronic And Catalytic Properties Of Low-Dimensional Carbon Nanomaterials

In this thesis, using the density functional theory, we have studied in detail the electronic properties of different graphene, silicene and carbon nanotube materials, and the catalytic properties of metal-free fullerenes clusters.In the study of the electronic properties of graphene materials, according to the different positions of Dirac cone in the pseudo graphene superlattices, we have divided the pseudo graphene superlattices into three categories: the four-fold degenerate?p,3m? rectangle pseudo superlattices, the other?p,3m±1? type rectangle pseudo superlattices, and arbitrary shape pseudo superlattices. Also, we have studied the electronic properties of these superlattices under uniaxial strain, the effects of degenerate perturbation in the sublattice equivalence preserved superlattices, the cooperative effects of uniaxial stain and degenerate perturbation, the effects of uniaxial stain on the sublattice equivalence breaking superlattices, respectively. Our results show that:?1? the uniaxial strain would make Dirac cone to move along the parth associated with the lattice type of superlattice;?2? the degenerate perturbation in the sublattice equivalence preserved superlattice shows a novel mechanism for opening band gap as compared to the one induced by the sublattice equivalence breaking;?3? the graphene based nanomaterials with inversion symmetry?such as the D6 h defect patterned graphene nanomeshes? can be switched between semiconductor and semi-metal by manipulating the uniaxial strain. In addition, due to the fact that silicene and graphene have analogous electronic properties, we also have investigated the electronic properties of silicene based nanomaterials, for which the conclusions are found to be consistent with those obtained for the corresponding graphene materials.In the study of the electronic properties of carbon nanotubes, firstly, we have analysized the strain effects carbon nanotubes and discussed the reason why some metallic carbon nanotube has finite band gaps opened. Then, we have respectively compared the effects of degenerate perturbations in the sublattice equivalence preserved nanotubes and the sublattice equivalence breaking ones. We found that these two kind of perturbations also have distinct effects on opening band gap in carbon nanotubes, which may benefit the studies on modulating the electronic properties of carbon nanotubes toward practical application demand.For the research of the catalytic properties of fullerene-based nanostructures, we have investigated the adsorption properties of CO and O2 on single B and N doped C₆₀ clusters, respectively. The ground-state configurations of five different B and N co-doped C₆₀ clusters and the adsorption properties of CO and O2 on these clusters have been carefully studied. The calculated minimum-energy pathway and the energy barrier for CO oxidation on C56BN3 cluster have also been discussed. Our results show that:?1? the doping of single B and N in fullerene can promote the CO oxidation reaction;?2? the B prefer to bond with N in the co-doped fullerene;?3? the C56BN3 cluster has a good catalytic activity for CO oxidation. Based on our studies, the B and N co-doped fullerene materials are found to have superior catalytic properties, suggesting a method to design novel metal-free catalysts.