calculations*

Transition metal oxide clusters are not only scientifically interesting, but they are also challenging systems to model using first principles approaches due to strong electron correlations and their open-shell character. These challenges are particularly noteworthy when modeling their excited state properties. The GW approximation using atom-centered localized basis sets has recently emerged as a reliable method for studying excited state properties of confined systems. Here, we investigate various flavors of the GW method (one-shot, eigenvalue self-consistent) with different starting points when applied to quasiparticle spectra of 3d transition metal dioxide cluster anions ScO₂^-, TiO₂^-, VO₂^-, CrO₂^-, MnO₂^-, FeO₂^-, NiO₂^-, and CuO₂^-. We compare predictions from different levels of theory with each other and with experimental photoelectron spectra.