  The accurate resolution of the chemical properties of strongly correlated
systems, such as biradicals, requires the use of electronic structure theories
that account for both multi-reference as well as dynamic correlation effects. A
variety of methods exist that aim to resolve the dynamic correlation in
multi-reference problems, commonly relying on an exponentially scaling
complete-active-space self-consistent-field (CASSCF) calculation to generate
reference molecular orbitals (MOs). However, while CASSCF orbitals provide the
optimal solution for a selected set of correlated (active) orbitals, their
suitability in the quest for the resolution of the total correlation energy has
not been thoroughly investigated. Recent research has shown the ability of
Kohn-Shan density functional theory (KS-DFT) to provide improved orbitals for
coupled cluster (CC) and M\o ller-Plesset perturbation theory (MP)
calculations. Here we extend the search for optimal and more cost effective MOs
to post-configuration-interaction (post-CI) methods, surveying the ability of
the MOs obtained with various DFT functionals, as well as Hartree-Fock, and CC
and MP calculations to accurately capture the total electronic correlation
energy. Applying the anti-Hermitian contracted Schr\"odinger equation (ACSE) to
the dissociation of N$_2$, the calculation of biradical singlet-triplet gaps
and the transition states of the bicylobutane isomerization, we demonstrate DFT
provides a cost-effective alternative to CASSCF in providing reference orbitals
for post-CI dynamic correlation calculations.
