| Abstract
| - We present a database of 21 bond dissociation energies for breaking metal−ligand bonds. The molecules inthe metal−ligand bond energy database are AgH, CoH, CoO+, CoOH+, CrCH3+, CuOH2+, FeH, Fe(CO)5,FeO, FeS, LiCl, LiO, MgO, MnCH3+, NiCH2+, Ni(CO)4, RhC, VCO+, VO, and VS. We have also createddatabases of metal−ligand bond lengths and atomic ionization potentials. The molecules used for bond lengthsare AgH, BeO, CoH, CoO+, FeH, FeO, FeS, LiCl, LiO, MgO, RhC, VO, and VS and the ionization potentialsare for the following atoms: C, Co, Cr, Cu, Ni, O, and V. The data were chosen based on their diversity andexpected reliability, and they are used along with three previously developed databases (transition metaldimer bond energies and bond lengths and main-group molecular atomization energies) for assessing theaccuracy of several kinds of density functionals. In particular, we report tests for 42 previously definedfunctionals: 2 local spin density approximation (LSDA) functionals, 14 generalized gradient approximation(GGA) methods, 13 hybrid GGA methods, 7 meta GGA methods, and 8 hybrid meta GGA methods. Inaddition to these functionals, we also examine the effectiveness of scaling the correlation energy by testing13 functionals with scaled or no gradient-corrected correlation energy, and we find that functionals of thiskind are more accurate for metal−metal and metal−ligand bonds than any of the functionals already in theliterature. We also present a readjusted GGA and a hybrid GGA with parameters adjusted for metals. Whenwe consider these 57 functionals for metal−ligand and metal−metal bond energies simultaneously with main-group atomization energies, atomic ionization potentials, and bond lengths we find that the most accuratefunctional is G96LYP, followed closely by MPWLYP1M (new in this article), XLYP, BLYP, and MOHLYP(also new in this article). Four of these five functionals have no Hartree−Fock exchange, and the other hasonly 5%. As a byproduct of this work we introduce a convenient diagnostic, called the B1 diagnostic, forascertaining the multireference character in a bond.
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