LANTHANIDE-BASED AND ACTINIDE-BASED FULLERITE COMPOUNDS - POTENTIAL-AXC60 SUPERCONDUCTORS

The stabilities of lanthanide and actinide intercalated fullerites are calculated with a Born-Hess thermodynamic cycle. For example, the calculated formation enthalpies indicate that the most likely superconducting phase of the Yb compound, Yb-2(2+) C-60(4-), is metastable and may decompose into the insulating Yb-3(2+) C-60(6-) and pristine C60 phases. Apart from the formation enthalpies, our calculations predict the equilibrium structure and stoichiometry, as well as intercalant valency, which are presently unknown in the Yb and other lanthanide and actinide intercalation compounds. We find some of these compounds, such as La-3(3+) C-60(9-), to be excellent candidates for a new class of C60 based superconductors.