Photoelectron spectra of early 3d-transition metal dioxide molecular anions from GW calculations

Photoelectron spectra of early 3d-transition metal dioxide anions, ScO2-, TiO2-, VO2-, CrO2-, and MnO2-, are calculated using semilocal and hybrid density functional theory (DFT) and many-body perturbation theory within the GW approximation using one-shot perturbative and eigenvalue self-consistent formalisms. Different levels of theory are compared with each other and with available photoelectron spectra. We show that one-shot GW with a PBE0 starting point (G(0)W(0)@PBE0) consistently provides very good agreement for all experimentally measured binding energies (within 0.1 eV-0.2 eV or less). We attribute this to the success of PBE0 in mitigating self-interaction error and providing good quasiparticle wave functions, which renders a first-order perturbative GW correction effective. One-shot GW calculations with a Perdew-Burke-Ernzerhof (PBE) starting point do poorly in predicting electron removal energies by underbinding orbitals with typical errors near 1.5 eV. A higher exact exchange amount of 50% in the DFT starting point of one-shot GW does not provide very good agreement with experiment by overbinding orbitals with typical errors near 0.5 eV. While not as accurate as G(0)W(0)@PBE0, the G-only eigenvalue self-consistent GW scheme with W fixed to the PBE level provides a reasonably predictive level of theory (typical errors near 0.3 eV) to describe photoelectron spectra of these 3d-transition metal dioxide anions. Adding eigenvalue self-consistency also in W, on the other hand, worsens the agreement with experiment overall. Our findings on the performance of various GW methods are discussed in the context of our previous studies on other transition metal oxide molecular systems.

Automated summary

The photoelectron spectra of early 3d-transition metal dioxide anions were calculated using different levels of DFT theory and GW approximation methods. The study found that using G(0)W(0) with a PBE0 starting point consistently provided good agreement with experimentally measured binding energies. Conversely, one-shot GW calculations with a PBE starting point performed poorly in predicting electron removal energies.