%0 Journal Article %T Towards a first-principles determination of effective Coulomb interactions in correlated electron materials: Role of intershell interactions %A Priyanka Seth %A Philipp Hansmann %A Ambroise van Roekeghem %A Loig Vaugier %A Silke Biermann %J Physics %D 2015 %I arXiv %X 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. %U http://arxiv.org/abs/1508.07466v1