Order-Disorder Transition in C₆₀: Possible Role of Stacking Faults

Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders, not in single crystals, of C₆₀ from which solvents and impurities had been carefully excluded. This is attributed to phase transformation facilitated by nucleation around stacking faults. This proposal is supported by internal friction measurements on films, which confirmed the presence of this secondary transition, and by x-ray diffraction, which detected an hcp structure within the fcc lattice of C₆₀ at room temperature.