  Facilitated by a rigorous partitioning of a molecular system's orbital basis
into two fundamental subspaces - a reference and an expansion space, both with
orbitals of unspecified occupancy - we generalize our recently introduced
many-body expanded full configuration interaction (MBE-FCI) method to allow for
electron-rich model and molecular systems dominated by both weak and strong
correlation to be addressed. By employing minimal or even empty reference
spaces, we show through calculations on the one-dimensional Hubbard model with
up to 46 lattice sites, the chromium dimer, and the benzene molecule how
near-exact results may be obtained in a entirely unbiased manner for chemical
and physical problems of not only academic, but also applied chemical interest.
Given the massive parallelism and overall accuracy of the resulting method, we
argue that generalized MBE-FCI theory possesses an immense potential to yield
near-exact correlation energies for molecular systems of unprecedented size,
composition, and complexity in the years to come.
