HETEROPHASE FLUCTUATIONS NEAR THE 260-K TRANSITION AND THE ABSENCE OFREFLECTIONS WITH HALF-INTEGER INDEXES IN A C-60 SINGLE-CRYSTAL

A diffuse-neutron-scattering investigation of the 260-K order-disorder transition in a C60 single crystal reveals the presence of ordered cl usters within a narrow temperature range above the transition temperat ure. This cluster state is metastable and gives evidence for heteropha se fluctuations. In addition, during an excursion to lower temperature s we investigate regions near reciprocal-lattice points with half-inte ger indices where recently additional superlattice intensities were re ported to have been observed by electron-microscopic methods. At three selected reciprocal-lattice points, i.e., (0.5,0.5,5.5), (2.5,2.5,0.5 ), and (3.5,3.5,5.5), no superlattice reflections can be found down to 10 K.