The Structure of Ternary Alkali Graphite Intercalation Compounds

Abstract

We have studied the structure of Rb_xK_1−x C₈ with x-rays. The major motivation of the work is to investigate the correlation in the positions of the alkali metal atoms in between the carbon layers. This is interesting because anomalies in the physical properties (magnetic susceptibility¹, Raman-active M-point phonon frequency², and elastic constant C ³₃₃ ) have been measured for x=0.67. Two different explanations have been proposed to account for these anomalies. Solin² postulated that short range order of the alkali metal atoms can account for the Raman data. Akera⁴ argues that the Van Hove singularity in the density of states at the Fermi level gives rise to the anomalies in the data. X-ray evidence for short range order will help distinguish between the two models.