Superconducting Carbon-Cage Network with T_c of 109 K at Ambient Pressure

A novel carbon-cage network was reported, denoted as C₁₈, found to be a low energy structure by first principles particle swarm structure search. The compound exhibits high temperature electron-phonon ambient pressure superconductivity with T_c = 79 K for elemental doping and can be raised to T_c = 109 K by appropriate hole doping. Analyses of the phonon spectra, molecular dynamics simulations, and enthalpy differences relative to analogous structures synthesized experimentally all suggest that the hole-doped high-T_c structure is a viable candidate for experimental synthesis.