Compressibility of M3C60 Fullerene Superconductors: Relation Between Tc and Lattice Parameter

Science  14 Feb 1992:
Vol. 255, Issue 5046, pp. 833-835
DOI: 10.1126/science.255.5046.833


X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K3C60 and Rb3C60, the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature Tc measured by other groups, establish a universal first-order relation between Tc and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.