  The determination of the effective Coulomb interactions to be used in
low-energy Hamiltonians for materials with strong electronic correlations
remains one of the bottlenecks for parameter-free electronic structure
calculations. We propose and benchmark a scheme for determining the effective
local Coulomb interactions for charge-transfer oxides and related compounds.
Intershell interactions between electrons in the correlated shell and ligand
orbitals are taken into account in an effective manner, leading to a reduction
of the effective local interactions on the correlated shell. Our scheme
resolves inconsistencies in the determination of effective interactions as
obtained by standard methods for a wide range of materials, and allows for a
conceptual understanding of the relation of cluster model and dynamical mean
field-based electronic structure calculations.
