<p>The
selection of density functional is the key to obtain useful results in a computational
work. Due to their complexity in terms of electronic structures, open-shell
first-row transition metal complexes are difficult to be correctly described by
most functionals. In this work, totally 19 reactions involving V, Cr, Mn, Fe,
Co, Ni complexes, either monometallic or bimetallic, were used as testing set
for 18 functionals ranging from generalized gradient approximation (GGA) to
doubly-hybrid functionals, with experimental electron affinities and ligand
association energies as standard. It is shown that for monometallic complexes
PBE0-D3BJ and B3LYP-D3BJ perform the best, whereas MN15 and MN15L are the
optimal functionals for bimetallic compounds. On the other hand, the accuracy
of DLPNO-CCSD(T) is not significantly better than the best-performing
functionals, and the use of doubly-hybrid functionals is risky.</p>
Assessing model-dielectric-dependent hybrid functionals on the antiferromagnetic transition-metal monoxides MnO, FeO, CoO, and NiO
