Hybrid QM / QM Study of Electronic d – d Spectra of Trivalent Transition Metal Oxides

ABSTRACT Transition metal oxides have been traditionally studied in theoretical chemistry and solid‐state physics as they reflect the complexity of the electronic structure of materials with open ‐shells. The complex electronic structure stems from the presence of strong correlations of both static and dynamical nature which are characteristic of open shell ‐electrons. Systematic and computationally efficient account for correlation effects in transition metal compounds is a key challenge in theoretical chemistry. Hybrid electronic structure methods represent a promising way to address this problem. In this work, we apply a hybrid QM/QM method—periodic Effective Hamiltonian of Crystal Field (pEHCF)—to study multiplet structure of open ‐shells in a series of trivalent and mixed‐valence oxides: ‐Fe 2 O 3 , ‐Mn 2 O 3 , Cr 2 O 3 and Co 3 O 4 . The calculated energies of the excited ‐multiplets are compared with available experimental optical spectroscopy data. Our calculations clarify the interpretation of spectroscopic lines observed in experiments for two challenging systems: Fe 2 O 3 and Co 3 O 4 . Furthermore, we assess the overall performance of pEHCF for transition metal oxides and place our results in a more general context by comparing them with previous studies that used different electronic structure methods.