The Holohedrization Effect in Ligand Field Models

The ligand field theory is an early and yet perennial class of quantum models accounting for the optical and magnetic properties of metal ions as a function of their environment in compounds. In the context of modern quantum chemistry, in order to predict properties from first principles, the ligand field paradigm can serve to illuminate the black box of heavy calculations, extracting heuristic meaning and causal roots. The genuine ligand field models are tacitly affected by an artificial feature, so-called holohedrization. It induces an inversion symmetry, even in cases where the local geometry does not show this element. This aspect received little attention over decades of using the ligand field Hamiltonians. In this work, we systematically investigate, assisted by state-of-the-art ab initio computer experiments, whether holohedrization is a hidden drawback of early models or if it also appears in realistic modeling. We found that the holohedrization trend also appears when using data from modern ab initio calculations.