PNNL

Abstract

report computations of the vertical ionization potentials within the GW approximation of the near-complete series of first-row transition metal (V-Zn) aqua ions in their most common oxidation states, i.e. V3+, Cr3+, Cr2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+. The d-orbital occupancy of these systems span a broad range from d2 to d10. All the structures were first optimized at the density functional theory level with explicit water molecules and surrounded by a continuum solvation model. Vertical ionization potentials were computed with the one-shot G0W0 approach on a range of transition metal ion clusters (6, 18, 40, and 60 explicit water molecules) and the convergence with respect to the basis set size was evaluated using the systems with 40 water molecules. We assess the results using three density functional approximations as starting points for the vertical ionization potential calculations, namely G0W0@PBE, G0W0@PBE0, and G0W0@r2SCAN. While the predicted ground-state structures are similar with all the exchange-correlation functionals, the vertical ionization potentials were in closer agreement with experiment when using the G0W0@PBE0 and G0W0@r2SCAN approaches, with the r2SCAN based calculations being significantly cheaper. Computed bond distances and vertical ionization potentials for all structures were compared with available experimental data and are in very good agreement.