On the use of smalld-spaces in SCF and CI calculations on transition metals

Summary

The possibility to use atomic basis sets with only twod-functions describing the metal atom has been investigated, both at the SCF and the CI levels, for the Ni and Pd atoms, their mono-hydrides and their mono-oxides. Using a general contraction scheme, two atomicd-orbitals, corresponding to two of the atomic configurationss ² d ⁸,s ¹ d ⁹ ands ⁰ d ¹⁰ were used as the twod-type basis functions. A surprisingly large part of the correlation effect on both atomic excitation energies and on the equilibrium distance and dissociation energies of the hydrides and the oxides was obtained using these small basis sets. It is argued that the reason for this is important “near-degeneracy” effects involving different atomicd-configurations and not dynamic correlation effects.