Structure of second-stage graphite–rubidium, C24Rb

Abstract

The X-ray diffraction patterns from second-stage rubidium–graphite, C₂₄Rb, have been measured at high resolution in the basal plane for samples made from oriented, exfoliated graphite. The pattern at 5 K has been indexed on the basis of both a simple static distortion wave and a √43 ×√43 superlattice consisting of nearly commensurate √7 ×√7 patches of alkalimetal ions bounded by domain walls. This model has been tested by least-squares refinement of all the observed intensities and peak positions and compared with the static distortion wave predictions. The C₂₄Rb system, because of the small domain size, turns out to be particularly suitable for comparing these approaches, which are seen here to be equivalent.