© The American Physical Society
Physical Review. B, Condensed Matter and Materials Physics, vol.87, article number 085402, 2013
American Physical Society
Density functional calculations of the electronic structure of the Fe12 cluster encapsulated inside finite singlewall
zigzag carbon nanotubes of indices (11,0) and (10,0) have been performed. Several Fe12 isomers have
been considered, including elongated shape isomers aimed to fit well inside the nanotubes, and the icosahedral
minimum energy structure. We analyze the structural and magnetic properties of the combined systems, and
how those properties change compared to the isolated systems. A strong ferromagnetic coupling between the
Fe atoms occurs both for the free and the encapsulated Fe12 clusters, but there is a small reduction (3–7.4μB)
of the spin magnetic moment of the encapsulated clusters with respect to that of the free ones (μ = 38μB).
The reduction of the magnetic moment is mostly due to the internal redistribution of the spin charges in the
iron cluster. In contrast, the spin magnetic moment of the carbon nanotubes, which is zero for the empty tubes,
becomes nonzero (1–3μB) because of the interaction with the encapsulated cluster. We have also studied the
encapsulation of atomic Fe and the growth of small Fen clusters (n = 2, 4, 8) encapsulated in a short (10,0) tube.
The results suggest that the growth of nanowires formed by distorted tetrahedral Fe4 units will be favorable in
(10,0) nanotubes and nanotubes of similar diameter.
