  A new approach, motivated by Fock space localization, for constructing a
reduced many-particle Hilbert space is proposed and tested. The self-consistent
Hartree-Fock (SCHF) approach is used to obtain a single-electron basis from
which the many-particle Hilbert space is constructed. For a given size of the
truncated many particle Hilbert space only states with the lowest number of
particle-hole excitations are retained and exactly diagonalized. This method is
shown to be more accurate than previous truncation methods, while there is no
additional computational complexity.
