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

Abstract

Photoelectron spectra of early 3d−transition metal dioxide anions, ScO − 2 , TiO − 2 , VO − 2 , CrO − 2 , MnO − 2 , 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 0.1-0.2 eV or less), which we attribute 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 semilocal exchange in the DFT starting point (e.g. G 0 W 0 @PBE) do poorly in predicting electron removal energies by underbinding orbitals with typical errors near 1.5 eV. Higher amounts of exact exchange (e.g. 50%) in the DFT starting point of one-shot GW do 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 (G n W 0 @PBE) 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 (G n W n @PBE), 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.