Interplay of single-wall carbon nanotubes and encapsulated $\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$

Encapsulations of metallofullerenes ($\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$) inside single-wall carbon nanotubes are investigated by using first-principles calculations. We found that $\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ are endothermically encapsulated inside the (17,0) nanotube, while the encapsulation processes are exothermic inside the (14,7) and (19,0) nanotubes. Electron transfer takes place from the nanotubes to strongly electrophilic $\mathrm{La}@{\mathrm{C}}_{82}$ and ${\mathrm{La}}_2@{\mathrm{C}}_{80}$. Dependent on the tube chirality, the Van Hove singularity positions of the nanotube may be significantly shifted by a local 3% radial strain induced by metallofullerene insertion.

Figure 1

(Color online) Optimized structures of (a) $\mathrm{La}@{\mathrm{C}}_{82}@(17,0)$, (b) ${\mathrm{La}}_2@{\mathrm{C}}_{82}@(17,0)$, (c) ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}@(17,0)$, (d) ${\mathrm{La}}_2@{\mathrm{C}}_{80}@(14,7)$, and (e) ${\mathrm{La}}_2@{\mathrm{C}}_{80}@(19,0)$. Red (black) ball, La; pink (gray) ball, Sc; yellow (white) ball, N.

Figure 2

Encapsulation energy $\Delta E$ per MF inside SWNTs. A simple linear interpolation shows that the encapsulation energies of $\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$ cross zero at the tube diameter of 13.7, 13.9, and 13.6 Å, respectively.

Figure 3

Electronic energy bands of MF@(17,0), $\mathrm{MF}=\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$.

Figure 4

Electronic energy bands of MF@(14,7), $\mathrm{MF}=\mathrm{La}@{\mathrm{C}}_{82}$, ${\mathrm{La}}_2@{\mathrm{C}}_{80}$, and ${\mathrm{Sc}}_3\mathrm{N}@{\mathrm{C}}_{80}$.