THE ORIENTATIONAL PHASE-TRANSITION IN SOLID BUCKMINSTERFULLERENE EPOXIDE (C60O)

Crystalline C60O, the first fullerene epoxide, has been studied using calorimetry and high resolution powder X-ray diffraction. At room temperature, C60O is orientationally disordered with a face-centered cubic lattice, a = 14.185 angstrom. Upon cooling, an orientational ordering transition at 278 K leads to a low temperature simple cubic phase. At 19 K, this phase is qualitatively similar to the orientationally ordered Pa3BAR phase of C60, with a = 14.062 angstrom, but with additional randomness due to a distribution of orientations of the oxygen bonds.