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Where are the potassium ions located in the compound K3C60?

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cluster Figure 1: The four stable geometric structures of the seven-atom cluster of argon, in order of increasing energy: (A) A pentagonal bipyramid. (B) A regular octahedron with one face capped by the seventh atom. (C) A regular tetrahedron with three of its faces capped by other atoms. (D) A trigonal bipyramid with two of its faces capped by other atoms; although this has the highest energy of the four structures, it is very close in energy to the tricapped tetrahedron.

In the compound $K_{3} C_{60}$ , the potassium ions are located in the interstitial spaces between the spherical fullerene molecules.1

Unlike endohedral fullerenes, where a metal atom is physically trapped inside the carbon cage, the alkali atoms in $K_{3} C_{60}$ reside outside the $C_{60}$ molecules. In this specific crystalline structure, the fullerene molecules are arranged in a face-centered cubic (fcc) lattice, and the potassium ions occupy the spaces between them. This arrangement is notable because $K_{3} C_{60}$ acts as a metal and exhibits superconductivity at low temperatures.21