The doorsill of fullerene

How difficult is it for a guest atom to cut through C60 fullerene? Using an iron atom as a representative “intruder”, we explored the “quasistatic” processes of the atom going into and out from C60 along 3-fold or 5-fold axis and investigated the geometrical, electronic structures, and energy changes in the processes. Encaging an iron atom through 3-fold axis was more favored, with a lower energy barrier of about 4.20 eV. As it moved into C60 along 3-fold axis, the Fe atom must cross over two thresholds. The higher is located inside the C60 but not the outside.