An EXAFS study on the local structure in the Na2CsC60 superconductor

Octahedral cations in Rb3C60: Reconciliation of conflicting evidence from different probes

“…Since the claim for off-centering of the octahedral cation was made solely based on the smaller-than-expected value of the (octahedral) alkali-carbon nearest-neighbour distances, the possibility for an underestimation of these distances due to having neglected third cumulant contributions in the calculations must be considered seriously. In fact, a third EXAFS study, of (non-isostructural) Na 2 CsC 60 , finds O-Cs centered, and not displaced [24]. That compound has a significantly smaller O-site Debye-Waller factor (due to both the larger Cs ion in the O-site and a smaller lattice parameter), evidently making third cumulant corrections unnecessary.…”

Current Issues of Intercalation and Superconductivity in Solid State Fullerenes

“…It is noted that the fccstructure is sustained in spite of the off-centered octahedral cations in the ammoniated compounds. An x-ray diffraction [13] and EXAFS [14] study on the conventional superconductors showed that the octahedral cations are on-centered. Thus the ammoniated materials are the first examples of fcc compounds containing off-centered octahedral cations.…”