EFFECT OF STACKING DISORDER ON THE ORIENTATIONAL ORDERING TRANSITION OF SOLID C-60

We determine the nature of stacking disorder in C-60 by comparing X-ra y powder diffraction patterns to simulated patterns of disordered crys tals produced by a Monte Carlo method. Several samples have been speci ally prepared by rapid precipitation to have small grain size and sign ificant stacking disorder. The diffraction patterns of these samples a re well described by considering the density of one-dimensional disord er and the crystallite size. We give evidence and propose an explanati on for the correlation found between stacking disorder and the appeara nce of new structure in the DSC endotherm of the C-60 orientational or dering transition, a phenomenon often observed for C-60 samples and no t previously well understood.