Investigation of the use of density functionals in second- and third-row transition metal dimer calculations

We explore the use of density functionals. in calculating the equilibrium distances, dissociation energies, and harmonic vibrational frequencies of the homonuclear diatomics of the second-row transition metals, platinum, and gold. The outermost s-d interconfigurational energies (ICEs) and the outermost s and d ionization potentials (IPs) were also calculated for the second- and third-row transition metal atoms. Compared with the first-row transition metal dimer calculations (J Chem Phys 2000,112, 545-553), the binding energies calculated using the combination of the Becke 1988 exchange and the one-parameter progressive correlation (BOP) functional and Becke's three-parameter hybrid (B3LYP) functional are in better agreement with the experiment. However, the pure BOP functional still gives the deep and narrow dissociation potential wells for the electron configurations containing high-angular-momentum open-shell orbitals. Analysis of the s-d ICEs. and the s and d IN suggests that the overestimation may be due to the insufficient long-range interaction between the outermost s and d orbitals in the exchange functional. The hybrid B3LYP functional seems to partly solve this problem for many systems by the incorporation of the Hartree-Fock exchange integral. However, this still leads to an erroneous energy gap between the configurations of fairly different spin multiplicity, probably because of the unbalance of exchange and correlation contributions. (C) 2001 John Wiley & Sons, Inc.