The structure of the C₆₀ molecule: X-ray crystal structure determination of a twin at 110 K

Single-crystal x-ray diffraction methods were used to determine the crystal and molecular structure of C₆₀ buckminsterfullerene. At 110 kelvin C₆₀ is cubic, apparent Laue symmetry m3m, but it exhibits noncrystallographic systematic extinctions indicative of a twin in which I(hkl) and I(khl) are superimposed. In fact, C₆₀ crystallizes with four molecules in space group T_h⁶-Pa3 of the cubic system (Laue symmetry m3) with lattice constant a = 14.052(5) angstroms (Å) at 110 kelvin. The twin components are equal. A given component, which has crystallographically imposed symmetry 3 (C_3i), displays an ordered structure of a truncated icosahedron. The five independent C=C bonds that join C₆ rings average 1.355(9) Å; the ten independent C-C bonds that join C₆ and C₅ rings average 1.467(21) Å. The mean atom-to-atom diameter of the C₆₀ molecule is 7.065(3) Å. The molecules are very tightly packed in the crystal structure, with intermolecular C⋯C distances as short as 3.131(7) Å.