Structural and magnetic properties of ${\text{Tc}}_n@{\text{C}}_{60}$ endohedral metalofullerenes: First-principles predictions

We use ab initio spin-density-functional calculations to study the equilibrium structure and magnetic properties of ${\text{Tc}}_n@{\text{C}}_{60}$ endohedral metalofullerenes. We find that ${\text{C}}_{60}$ can endohedrally accommodate ${\text{Tc}}_n$ clusters with up to $n=7$ atoms, even though the encapsulation process becomes increasingly endothermic beyond $n=4$. The encapsulation does not change significantly the structure of the enclosed clusters, but reduces the magnetic moment due to a stronger Tc-C hybridization for the larger clusters.

Figure 1

(Color online) Ball-and-stick models of the equilibrium structures of free ${\text{Tc}}_n$ $\left(n=2–7\right)$ clusters computed at the GGA/PW91 level of theory. Additional information listed includes the calculated bond distances (in angstrom), total spin, and point-group symmetry.

Figure 2

(Color online) Ball-and-stick models of the equilibrium structure of ${\text{Tc}}_n@{\text{C}}_{60}$ endohedral metalofullerenes (left) and the frozen substructure of the encapsulated ${\text{Tc}}_n$ clusters (right) calculated at the GGA/PW91 level of theory. Additional information listed includes the calculated bond distances (in angstrom) and point-group symmetry of the encapsulated clusters.

Figure 3

(Color online) Dependence of the encapsulation energy $\Delta E_n$, associated with the ${\text{Tc}}_n+{\text{C}}_{60}\to {\text{Tc}}_n@{\text{C}}_{60}$ reaction, on the cluster size $n$.

Figure 4

(Color online) Dependence of the total electronic magnetic moment $\mu$ in free ${\text{Tc}}_n$ clusters and in ${\text{Tc}}_n@{\text{C}}_{60}$ endohedral metalofullerenes on the cluster size $n$.

Figure 5

(Color online) Cross sections of the total electron charge density $\rho$ of (a) $\text{Tc}@{\text{C}}_{60}$, (b) ${\text{Tc}}_2@{\text{C}}_{60}$, (c) ${\text{Tc}}_3@{\text{C}}_{60}$, and (d) ${\text{Tc}}_4@{\text{C}}_{60}$. The charge density is computed at the GGA/PW91 level of theory and plotted in $e/{\text{Å}}^3$ units.