  We present a new density-matrix functional within the recently introduced
framework for tensor-product expansions of the two-particle density matrix. It
performs well both for the homogeneous electron gas as well as atoms. For the
homogeneous electron gas, it performs significantly better than all previous
density-matrix functionals, becoming very accurate for high densities and
outperforming Hartree-Fock at metallic valence electron densities. For isolated
atoms and ions, it is on a par with previous density-matrix functionals and
generalized gradient approximations to density-functional theory. We also
present analytic results for the correlation energy in the low density limit of
the free electron gas for a broad class of such functionals.
