Methane-intercalated C-60: Preparation, orientational ordering, and structure

The orientational ordering temperature for methane-intercalated C-60 is greatly depressed from similar to 260 K in pure C-60 to similar to 241 and similar to 235 K in the stable compounds C-60-CH4 and C-60-CD4, respectively. C-13 NMR shows that the C-60 molecules have ordered near 200 K while H-2 NMR shows that the CD4 continues to be completely unoriented and freely rotating. The Rietveld refinement of the structures of C-60-CD4 at 15, 200, and 296 K using time-of-flight neutron powder data as well as least squares refinement of Mo-K-alpha x-ray data on C-60-CH4 single crystals are consistent with such rotational disorder.