ON THE ACCURACY OF GRADIENT-CORRECTED DENSITY-FUNCTIONAL METHODS FOR TRANSITION-METAL COMPLEXES

Density functional theory with gradient corrections (DFTG) is applied to a series of second-row transition metal compounds. The mean absolute deviations from experiment for the atomic excitation energies and ionization potential are in the range 0.2-0.4 eV. In comparison with accurate multireference configuration interaction (MR-CI) and parametrized CI with parameter 80 (PCI-80) results for the binding energies of the MCH2 + cations, the mean absolute deviation is 6.7 kcal/mol to be compared with 17.8 kcal/mol at the modified coupled pair functional (MCPF) level. The DFTG result is more sensitive to the choice of asymptote with a mean deviation of 14 kcal/mol if the bonding atomic state is not used as asymptote. Product energies and transition states for the addition of methane to RhXL (X=H, Cl, L=H2O, NH 3, PH3, and CO) also show the same trends as the PCI-80 comparison and represent an improvement over the MCPF results. © 1995 American Institute of Physics.