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An effective core potential investigation of Ni, Pd, and Pt and their monohydrides

1986; American Institute of Physics; Volume: 85; Issue: 3 Linguagem: Inglês

10.1063/1.451839

1520-9032

Celeste McMichael Rohlfing, P. Jeffrey Hay, Richard L. Martin,

Advanced Physical and Chemical Molecular Interactions

The nickel, palladium, and platinum atoms and their monohydrides are investigated using effective core potentials (ECP’s) recently introduced by Hay and Wadt [J. Chem. Phys. 82, 270, 299 (1985)]. The palladium and platinum ECP’s include relativistic effects. Two types of ECP’s, which differ in their definition of the core region, are used in conjunction with large valence basis sets including f functions. Electron correlation is incorporated by Mo/ller–Plesset perturbation theory through fourth order. The results demonstrate the success of the ECP approximation: they are similar in quality to those of all-electron studies and at the same time are achieved at a reduced computational cost. Total correlation energies obtained with both types of ECP’s are compared, and are found to be very sensitive to details of the basis set. Correlation effects are treated more consistently by the ECP’s which include the outermost core orbitals in the valence region. The relative ordering of molecular states is calculated to be 2Δ<2Π≈2Σ+ for NiH, 2Σ+<2Δ<2Π for PdH, and 2Δ≈2Σ+<2Π for PtH. Trends in bond lengths and bond strengths in the nickel, palladium, and platinum series are discussed.