DFT calculations on non-periodic clusters were also performed using CP2K, using the wavelet Poisson solver. The calculations used identical cutoff values as the periodic DFT calculations above, but employed different types of basis sets: In order to allow for an extrapolation to the complete basis set limit, as done in the ORCA calculations, triple-zeta and quadruple-zeta basis sets were included, using TZVP-GTH, TZV2P-GTH, QZV2P-GTH, and QZV3P-GTH basis sets from the GTH_BASIS_SETS file included in the CP2K distribution. To allow for better comparability with other parts of the study, calculations on clusters were also done with TZVP-MOLOPT-GTH basis sets, but these results were not included in the basis set extrapolation. The extrapolation to the CBS limit used a cubic extrapolation formula: