Hydrogen-induced magnetism in carbon nanotubes

Spin-polarized density functional theory is used to investigate hydrogen-induced magnetism in single-walled carbon nanotubes (SWNTs). Hydrogen trapped at a carbon vacancy can trigger delocalized $\pi$ electron spin polarization on semiconducting zigzag SWNTs. Hydrogen pinned by a carbon adatom on the surface of the SWNT can induce spin polarization localized at the carbon adatom, independent of the diameter and chirality of the tube.

Figure 1

(Color online) H-vacancy complex structures on the zigzag [(a) and (b)] and armchair [(c) and (d)] SWNTs. (a) and (c) are of the “perpendicular” configuration (HV-Per). (b) and (d) are of the “parallel” configuration (HV-Par). The red spheres represent hydrogen atoms.

Figure 2

(Color online) The isosurfaces of the spin density on the (8, 0) SWNT with an HV-Per complex from the front view (c) [structure (a)] and the side view (d) [structure (b)]. The red spheres represent hydrogen atoms.

Figure 3

(a) The band structure of the (8, 0) SWNT with a “perpendicular” vacancy (V-Per). (b) The band structure of the (8, 0) SWNT after the dangling bond at the “perpendicular” vacancy is saturated by a hydrogen atom (HV-Per). (c) The band structure of the (8, 0) SWNT after an extra electron is doped into the HV-Per vacancy.

Figure 4

(Color online) (a) The structure of the 1Ha H-vacancy complex on the (10, 0) SWNT and (b) the isosurface of the spin density. (c) The spin density contour projected on the plane formed by the $\mathrm{C}\mathrm{-}\mathrm{H}$ bond and the axis of the tube. The red spheres represent hydrogen atoms.

Figure 5

(Color online) The structures of the 2Ha (a), 2Hc (c), and 3Hd (d) H-vacancy complexes on the (10, 0) SWNT. The isosurfaces of spin density of the 2Ha (b), the positive (e), and negative (f) spin density of the 3Hd. The red spheres represent hydrogen atoms.

Figure 6

(Color online) H-vacancy complex structures on the (5, 5) SWNT with two [(a) and (b)] and three (c) hydrogen atoms. The red spheres represent hydrogen atoms.

Figure 7

(Color online) The front view (a) and the side view (b) of the (5, 5) SWNT with a carbon adatom of which one dangling bond is saturated by a hydrogen atom. (c) The side view of the distribution of the spin density that is highly localized at the carbon adatom. The red spheres represent hydrogen atoms.