Hongcun Bai

Doping the Buckminsterfullerene by Substitution: Density Functional Theory Studies of C59X (X = B, N, Al, Si, P, Ga, Ge, and As)

The heterofullerenes C59X (X = B, N, Al, Si, P, Ga, Ge, and As) were investigated by quantum chemistry calculations based on density functional theory. These hybrid cages can be seen as doping the buckminsterfullerene by heteroatom substitution. The geometrical structures, relative stabilities, electronic properties, vibrational frequencies, dielectric constants, and aromaticities of the doped cages were studied systemically and compared with those of the pristine C60 cage. It is found that the doped cages with different heteroatoms exhibit various electronic, vibrational, and aromatic properties. These results imply the possibility to modulate the physical properties of these fullerene-based materials by tuning substitution elements.

Zigzag Single-Walled Carbon Nanotubes Substitutionally Doped by Silicon: A Density Functional Theory Study

In this article, the nanotubes obtained by silicon atoms substitutionally doping the single-walled carbon nanotubes were investigated by quantum chemistry calculations under the framework of density functional theory. The geometrical structures, relative stabilities and electronic properties of the Si-doped tubes were studied in details and compared with those of the pristine (12, 0) tubes. It is found that the Si atoms in the doped tubes have obviously larger π-orbital axis vector angles than carbon atoms, and they also tend to “pop out” from the original positions. The Si-doped nanotubes exhibit lower thermodynamic stability than those of the undoped tubes from the viewpoint of both cohesive energy and Gibbs free energy. The energy levels of the frontier orbitals vary within 0.25 eV when the silicon atom is introduced into the nanotubes. However, most hybrid nanotubes present larger energy gaps than those of the pristine ones.

Theoretical Investigations on the Geometrical Structures, Energies, and Electronic Properties of the Heterofullerenes Made of the Smallest Fullerene

In this paper, the heterofullerenes made of the smallest fullerene, C20 were investigated by quantum chemistry calculations based on density functional theory. The geometrical structures, energies, electronic properties, and the aromaticities of the C19X (X = B, N, O, Al, Si, P, S, Ga, Ge, As, and Se) cages were studied systemically and compared with those of the pristine C20 cage. It is found that the doped cages with different heteroatoms exhibit various structural, electronic, and aromatic properties. Several doping behaviors of the C19X cages are different from those of the C59X cages. These results imply the possibility to modulate the physical properties of heterofullerenes by tuning the sizes of the carbon cages as well as the substitution elements.

Doping the armchair single-walled carbon nanotubes by silicon substitutions: A density functional theory study

In this paper the nanotubes obtained by silicon atoms substitutionally doping the armchair single-walled carbon nanotubes were investigated by quantum chemistry calculations under the framework of density functional theory. The geometrical structures, relative stabilities and electronic properties of the fifteen Si-doped tubes were studied in details and compared with those of the pristine (5, 5) tubes. It is found that the Si atoms tend to “pop out” from the original positions when the silicon atoms are introduced into the nanotubes. The Si-doped nanotubes exhibit lower thermodynamic stability than those of the undoped tubes from viewpoint of cohesive energy, and this is similar to the case of the silicon doped zigzag nanotubes. The energy levels of the frontier orbitals vary very little when the silicon atom is introduced into the nanotubes. However, most hybrid nanotubes present smaller energy gaps than those of the pristine ones.

Charge mobility modification of semiconducting carbon nanotubes by intrinsic defects

Charge carrier mobility is a central transport property in nanoscale electronics. Carbon nanotubes (CNTs) are supposed to have high carrier mobility. The preparation methods of CNTs have been greatly improved, but the defects always exist. This work presented first-principle investigations on the charge carrier mobility of carbon nanotubes containing several intrinsic defects. The charge carrier mobilities of zigzag (10, 0) tubes with Stone–Wales, mono vacant and 5/8/5 defects were studied as an example to explore the role of defects. Most carrier mobilities were decreased, but several values of mobility are unexpectedly increased upon the appearance of the defects. This interesting result is discussed based on the changes of the stretching modulus, the effective mass of the carrier and deformation potential constant induced by the defects.