Superconductivity in the Doped Polymerized Fullerite Clathrate from First Principles

Superconductivity in the new polymerized C-60 fullerite clathrate doped with simple metals is investigated through density functional theory methods. The phonon dispersion curves are systematically computed for the clathrate structures containing the guest dopants (Li, Na, K, Be, Mg, Ca, Al, Ga, Ge) in one of the two distinct cages, fullerene-like C-60 and sodalite-like C-24, exhibited by this structure. Only four of these structures, Li@C-24, Na@C-24, Ga@C-24, and Be@C-60, are dynamically stable in the harmonic approximation. They all show superconducting behavior, although their critical temperatures are predicted to be below 2 K.