Edge states in horseshoe-shape carbon nanotubes transformed by hydrogen adsorption

Abstract

We have investigated hydrogenated single-wall armchair (n,n) carbon nanotubes (CNTs) with 4 n 12 by using density functional theory calculations. Hydrogen adsorption may transform the CNTs into a horseshoe shape. Nonmagnetic edge-localized electron states have been identified in CNTs of horseshoe shape in this work. The σ -bond-like orbital overlaps across the edge-localized electrons, which sustain the horseshoe shape of the CNTs and hinder spontaneous unravelling into a graphene nanoribbon, cause the horseshoe-shape CNTs to become nonmagnetic metal. The bonding energy between the hydrogenated edges increases with the CNT diameter, approaching a limit of ∼1 eV.

Electronic structure of single-crystallineNdO0.5F0.5BiS2studied by angle-resolved photoemission spectroscopy

“…This proposal is supported by several magnetic penetration depth measurements on this family of superconductors, which all argued that the BiS 2 -based superconductors are the conventional s-wave type superconductors with fully developed gaps [14][15][16] . However, a recent neutron scattering work suggested that the e-ph coupling in LaO 0.5 F 0.5 BiS 2 could be much weaker than expected 17 . Band calculations found that the Fermi surface of LaO 0.5 F 0.5 BiS 2 is quasi-one-dimensional, which would provide a good nesting condition.…”

Search and design of nonmagnetic centrosymmetric layered crystals with large local spin polarization

“…The nominal centrosymmetric structure P4/nmm (T 0 ) structure, which has equal Bi-S 1 bonds in x-y plane, was used in X-ray refinement of the crystal structure of the prototype material LaBiOS 2 first in 1995 22 , and in many other following experiments [23][24][25] . However, recently it was shown theoretically that phonon instability will make the two in-plane Bi-S 1 bonds in the assumed P4/nmm structure LaOBiS 2 non equivalent 26 so as to remove the instability.…”

Edge-state magnetism in hydrogenated armchair carbon nanotubes

“…As shown in Fig. 4(a) by the asterisks, DE of (n,n)CNT-H0z is at best 10 meV, as is the case for (8,8)CNT-HNz for N 3, and gradually decreases with increasing n. (n,n)CNT-H(2nÀ1)z, which is expected to have the BE part only, is known to be transformed into a horseshoe shape of a nonmagnetic metal [16,17] and thus DE for the BE part only was not obtained. Instead, DE was investigated for a fixed width of the BE part and for a fixed width of the ZE part as a function of the width of the opposite part, only the contribution from the part with a fixed width being expected to survive at large widths of the opposite part.…”

“…The BE part enlarges with N, reducing the ZE part, and only bearded edges will remain when N ¼ (2nÀ1). However, in practice, (n,n) CNT-H(2nÀ1)z, in which hydrogen atoms are adsorbed on the CeC pairs perpendicular to the tube axis, is known to be transformed into a horseshoe-shape of nonmagnetic metal [16,17], which is out of the scope of this work.…”