Ferromagnetism of an all-carbon composite composed of a carbon nanowire nside a single-walled carbon nanotube

Using the first-principles spin density functional approach, we have studied magnetism of a new type of all-carbon nanomaterials, i.e., the carbon nanowires inserted into the single-walled carbon nanotubes. It is found that if the 1D carbon nanowire density is not too higher, the ferromagnetic ground state will be more stable than the antiferromagnetic one, which is caused by weak coupling between the 1D carbon nanowire and the single-walled carbon nanotube. Also, both dimerization of the carbon nanowire and carbon vacancy on the tube-wall are found to enhance the magnetic moment of the composite.Comment: 3 figure

Structural transformations of double-walled carbon nanotube bundle under hydrostatic pressure

Three kinds of the response mechanisms to the external pressure have been found for double-walled carbon nanotube (DWNT) bundle, depending strongly on their average radius and symmetry. The small-diameter DWNT bundle undergoes a small discontinuous volume change, and then deform continuously. The intermediate-diameter DWNT bundle collapses completely after a structure phase transition (SPT). Significantly, two SPTs exist for the larger-diameter DWNT bundle if the outer tube has no $C_{6}$ or $C_{3}$ symmetry. It would be interesting to search for signatures of these different structural transformations by experimentally investigating mechanical, optical and thermal response functions of DWNT bundle.Comment: 9 pages, 2 figure

Single-walled carbon nanotube bundle under hydrostatic pressure studied by the first-principles calculations

The structural, electronic, optical and vibrational properties of the collapsed (10,10) single-walled carbon nanotube bundle under hydrostatic pressure have been studied by the first-principles calculations. Some features are observed in the present study: First, a collapsed structure is found, which is distinct from both of the herringbone and parallel structures obtained previously. Secondly, a pseudo-gap induced by the collapse appears along the symmetry axis \textit{$\Gamma$X}. Thirdly, the relative orientation between the collapsed tubes has an important effect on their electronic, optical and vibrational properties, which provides an efficient experimental method to distinguish unambiguously three different collapsed structures.Comment: 14 pages, 6 figure

Geometrical and electronic structures of the (5, 3) single-walled gold nanotube from first-principles calculations

The geometrical and electronic structures of the 4 {\AA} diameter perfect and deformed (5, 3) single-walled gold nanotube (SWGT) have been studied based upon the density-functional theory in the local-density approximation (LDA). The calculated relaxed geometries show clearly significant deviations from those of the ideally rolled triangular gold sheet. It is found that the different strains have different effects on the electronic structures and density of states of the SWGTs. And the small shear strain can reduce the binding energy per gold atom of the deformed SWGT, which is consistent with the experimentally observed result. Finally, we found the finite SWGT can show the metal-semiconductor transition.Comment: 11 pages, 4 figure