Orientational Disorder in Solvent-Free Solid C70

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Science  29 Nov 1991:
Vol. 254, Issue 5036, pp. 1350-1353
DOI: 10.1126/science.254.5036.1350


The high-temperature structure of solvent-free C70 has been determined with high-resolution x-ray powder difraction and electron microscopy. Samples crystallized from solution form hexagonal close-packed crystals that retain an appreciable amount of residual toluene, even after prolonged heating. Samples prepared by sublimation, which contain no detectable solvent, are primarily face-centered cubic with some admixture of a hexagonal phase. The relative volume of the hexagonal phase can be further reduced by annealing. The structures of both phases are described by a model of complete orientational disorder. The cubic phase contains an appreciable density of stacking faults along the [111] direction.

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