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We gauge the importance of self-interaction errors in density functional approximations (DFAs) for the case of water clusters. To this end, we used the Fermi–Löwdin orbital self-interaction correction method (FLOSIC) to calculate the binding energy of clusters of up to eight water molecules. Three representative DFAs of the local, generalized gradient, and metageneralized gradient families [i.e., local density approximation (LDA), Perdew–Burke–Ernzerhof (PBE), and strongly constrained and appropriately normed (SCAN)] were used. We find that the overbinding of the water clusters in these approximations is not a density-driven error. We show that, while removing self-interaction error does not alter the energetic ordering of the different water isomers with respect to the uncorrected DFAs, the resulting binding energies are corrected toward accurate reference values from higher-level calculations. In particular, self-interaction–corrected SCAN not only retains the correct energetic ordering for water hexamers but also reduces the mean error in the hexamer binding energies to less than 14 meV/${\mathrm{H}}_2\mathrm{O}$from about 42 meV/${\mathrm{H}}_2\mathrm{O}$for SCAN. By decomposing the total binding energy into many-body components, we find that large errors in the two-body interaction in SCAN are significantly reduced by self-interaction corrections. Higher-order many-body errors are small in both SCAN and self-interaction–corrected SCAN. These results indicate that orbital-by-orbital removal of self-interaction combined with a proper DFA can lead to improved descriptions of water complexes.

We present candidate structures for the most stable isomers for the VSc₂N@C₇₀, VSc₂N@C₇₆, VSc₂N@C₇₈, and VSc₂N@C₈₀using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search correctly identifies the experimentally observed VSc₂N@C₈₀isomer as the most stable structure. The structural analysis shows that only VSc₂N@C₇₀has a non‐IPR cage among the four endohedral fullerenes. Respectively, VSc₂N@C₇₀and VSc₂N@C₇₆have nearly degenerate spin states with total spinS= 0 andS= 1. All the lowest energy cages are energetically stable and show significant electron accepting capacity comparable to C₆₀.