  Density-functional theory is applied to compute the ground-state energies of
quantum hard-sphere solids. The modified weighted-density approximation is used
to map both the Bose and the Fermi solid onto a corresponding uniform Bose
liquid, assuming negligible exchange for the Fermi solid. The required
liquid-state input data are obtained from a paired phonon analysis and the
Feynman approximation, connecting the static structure factor and the linear
response function. The Fermi liquid is treated by the Wu-Feenberg cluster
expansion, which approximately accounts for the effects of antisymmetry.
Liquid-solid transitions for both systems are obtained with no adjustment of
input data. Limited quantitative agreement with simulation indicates a need for
further improvement of the liquid-state input through practical alternatives to
the Feynman approximation.
