  The electronic structure and electron-phonon coupling in Y2C3 is investigated
using density functional calculations. We find that the Fermi level falls in a
manifold of mixed character derived from Y d states and antibonding states
associated with the C dimers in the structure. Calculations of the
electron-phonon coupling for Y and C modes show that the former provide most of
the coupling. Modes associated with C-C bond stretching have large matrix
elements, but make small contributions to the coupling because of their high
phonon frequencies. Substantial electron doping of the C-C antibonding states
would yield a large increase in the coupling and critical temperature, perhaps
to values comparable to MgB2. However, it seems unlikely that a modification of
Y2C3 with much higher filling of the C-C antibonding states can be stabilized.
