  We present a variational ansatz for the ground state of a strongly correlated
Bose system. This ansatz goes beyond the Jastrow-Feenberg functional form and
explicitly enforces coordination shells in the structure of the wavefunction.
We apply this ansatz to liquid helium-4 with a simple three-variable
parametrization of the pair functions. The optimized wavefunction is found to
give an excellent description of the mid-range correlations in the fluid. We
also demonstrate the possibility to use this ansatz to study inhomogeneous
systems. The phase separation and free surface emerge naturally in this
wavefunction, even though it is constructed of short-range two-body functions
and does not contain one-body terms. Because no explicit description of the
surface is necessary, this provides a powerful description tool for cluster
states.
