XAFS study of bcc fullerene compounds, Rb₆C₆₀, Ba₆C₆₀ and K₃Ba₃C₆₀

Rb K-edge XAFS of Rb₆C₆₀ and Ba K-edge XAFS of Ba₆C₆₀ and K₃Ba₃C₆₀ have been studied, all of which take a bcc structure. The radial structure functions obtained by Fourier transform of XAFS spectra for these compounds showed two pronounced envelopes which can be attributed to the scattering between metal ion and the neighboring C atoms and that between metal ions. The mean-square-displacements for the metal-C in these compounds were larger than that for the t-site Rb-C in Rb₃C₆₀ because of the distribution in metal-C distances. From the temperature dependent XAFS, it has been found that the mean-square-displacement for Rb-C in a non-superconductor Rb₆C₆₀ shows no anomaly around superconducting transition temperature, contrary to a superconductor Rb₃C₆₀.