RESUMO
The electronic structure of graphitic cones exhibits distinctive topological features associated with the apical disclinations. Ahranov-Bohm magnetoconductance oscillations (period Phi(0)) are completely absent in rings fabricated from cones with a single pentagonal disclination. Close to the apex, the local density of states changes qualitatively, either developing a cusp which drops to zero at the Fermi energy, or forming a region of nonzero density across E(F), a local metallization of graphite.
RESUMO
The well-defined geometry and extreme structural anisotropy of a multiwalled carbon nanotube can bring qualitatively new features to its nanometer-scale tribology. Efficient cancellation of registration-dependent interactions in incommensurate tubes (and also, surprisingly, certain axial commensurate tubes) can induce extremely small and nonextensive shear strengths.
RESUMO
Squashing brings circumferentially separated areas of a carbon nanotube into close proximity, drastically altering the low-energy electronic properties and (in some cases) reversing standard rules for metallic versus semiconducting behavior. Such a deformation mode, not requiring motion of tube ends, may be useful for devices. Uniaxial stress of a few kbar can reversibly collapse a small-radius tube, inducing a 0.1 eV gap with a very strong pressure dependence, while the collapsed state of a larger tube is stable. The low-energy electronic properties of chiral tubes are surprisingly insensitive to collapse.
RESUMO
Helium atoms are strongly attracted to the interstitial channels within a bundle of carbon nanotubes. The strong corrugation of the axial potential within a channel can produce a lattice gas system wherein the weak mutual attraction between atoms in neighboring channels induces a transition to an anisotropic condensed phase. At low temperatures, the specific heat of the adsorbate phase (with fewer than 2% of the atoms) greatly exceeds that of the host.
