Orientational Order and Electron Density of C60 at Room Temperature Studied by Combined Neutron and X-Ray Diffraction on Single Crystals

Abstract

Neutron and x-ray diffraction experiments have been performed on sublimation grown high-quality C60 single crystals, yielding complete data sets of Bragg intensities. Structure factors were first phased by fitting a spherical model of the C60 molecules. High resolution 3-dim densities were then reconstructed using Maximum Entropy, yielding consistent results concerning an orientational order of C60 in the high temperature phase. Besides the main effect (about 90%) consisting of an isotropic distribution, we have found clear evidence for an additional modulation of both nuclear and electron densities, and consistent with results first published by Chow et al. We propose a simple model to describe this effect.