The original version of this Article contained an error in the fifth sentence of the first paragraph of the ‘Application on H₂’ section of the Results, which incorrectly read ‘The role of electron correlation is quite apparent in this presentation: Fig. 1a is empty for the uncorrelated Hartree–Fock wave function, since projection of the latter wave function onto the 2pσ_u orbital is exactly zero, while this is not the case for the fully correlated wave function (Fig. 1d); also, Fig. 1b, c for the uncorrelated description are identical, while Fig. 1e, f for the correlated case are significantly different.’ The correct version replaces ‘Fig. 1e, f’ with ‘Fig. 2e and f’.