Boron nitride fullerene ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ doped with transition metal atoms: First-principles calculations

We perform first-principles calculations for the interaction of the transition metal atoms Fe, Co, and W, as well as the FeO molecule, with the boron nitride fullerene ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$. The stable structure of the atom-fullerene complexes may have the dopant atom either at the center of the cage or making covalent bonds with the fullerene wall, with similar total energies. We also find that the FeO molecule has a binding energy with the fullerene $2.5\mathrm{eV}$ larger than those of the transition metal atoms, and that it produces larger distortions in the cage. The electronic structure changes upon doping with the presence of several gap states. No magnetic moment is induced on the BN cage and, in general, the hybrid structures have the same magnetic moments as the isolated dopants.

Figure 1

(Color online) Highest-symmetry axes of ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ fullerene: directions 100, 011, and 111, corresponding to the line crossing the tetragonal ring, the line crossing the BN bond, and the line passing through the hexagonal ring, respectively. Black (blue) and gray (green) circles represent N and B atoms, respectively.

Figure 2

(a) Relaxed structure of an FeO molecule interacting with the ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ along the direction 011. Black circles and small gray ones represent N and B atoms, respectively; the large gray circle and the white one represent the Fe and the O atom, respectively. (b) Electronic density corresponding to gap states.

Figure 3

Projected density of states (PDOS) of several systems: (a) the isolated ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ and isolated Fe atom; (b) ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ doped with an Fe atom at the center of the cage; (c) ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ doped with an Fe atom at position ${100}_{\mathit{out}}$; (d) ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ doped with an Fe atom at position ${011}_{\mathit{out}}$; (e) ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$ doped with an FeO molecule as shown in Fig. 2a. Positive and negative values represent the DOSs projected on the spin up and down, respectively. From (a) to (e) the filled and the dashed lines represent the DOSs projected on the B and N atoms, respectively. In the doped fullerenes, the projection is only on B and N atoms closest to the adatom. From (a) to (e) the gray lines are the DOSs projected on the dopants. The vertical dashed lines are the HOMO and LUMO of the isolated ${\mathrm{B}}_{36}{\mathrm{N}}_{36}$