  The interaction and exchange-correlation contributions to the ground-state
energy of an arbitrary many-electron system can be obtained from a spherical
average of the wavevector-dependent diagonal structure factor (SF). We model
the continuous-k spherically averaged SF using quantum Monte Carlo calculations
in finite simulation cells. We thus derive a method that allows to
substantially reduce the troublesome Coulomb finite-size errors that are
usually present in ground-state energy calculations. To demonstrate this, we
perform variational Monte Carlo calculations of the interaction energy of the
homogeneous electron gas. The method is, however, equally applicable to
arbitrary inhomogeneous systems.
