Existence of high-order superlattices in orientationally orderedC60

We correlate the presence or absence of high-order modulated structures in solid ${\mathrm{C}}_{60}$ with the differential scanning calorimetry signature of the orientational ordering transition and other diagnostic data. We have searched for, but not observed, the 2a face-centered cubic structure recently observed in low-temperature electron and single-crystal x-ray diffraction. We conclude that the intrinsic ground state is the previously reported simple cubic structure [space group Pa3¯, a(14 K)=14.06 Å], and that other structures may be stabilized by defects or impurities.