  Understanding electron correlation is crucial for developing new concepts in
electronic structure theory, especially for strongly correlated electrons. We
compare and apply two different approaches to quantify correlation
contributions of orbitals: Quantum Information Theory (QIT) based on a Density
Matrix Renormalization Group (DMRG) calculation and the Method of Increments
(MoI). Although both approaches define very different correlation measures, we
show that they exhibit very similar patterns when being applied to a
polyacetelene model system. These results suggest one may deduce from one to
the other, allowing the MoI to leverage from QIT results by screening
correlation contributions with a cheap ("sloppy") DMRG with a reduced number of
block states. Or the other way around, one may select the active space in DMRG
from cheap one-body MoI calculations.
