Spin-free relativistic no-pair ab initio core model potentials and valencebasis sets for the transition metal elements Sc to Hg. Part I

Relativistic one-component ab initio core model potentials are presented fo r first-, second-, and third-row transition elements; corresponding valence spaces comprise the ns, (n-1) d, and (n-1) p shells. Direct relativistic e ffects on the valence electrons are explicitly taken into account by using one-component relativistic kinetic energy and Douglas-Kroll transformed no- pair nuclear attraction interaction operators. The Coulombic part of the at omic core-valence interaction has been fitted to the corresponding all-elec tron mean-field operators whereas a matrix representation has been chosen f or the exchange part. While not involved in the fitting process, all-electr on orbital energies and radial expectation values of the valence orbitals a re very well reproduced in atomic model potential calculations. Molecular t est calculations have been performed on selected transition metal oxides. E mploying a [4s, 4p, 4d] contraction of the valence basis, excellent agreeme nt between core model potential and all-electron no-pair results is achieve d for bond distances, harmonic frequencies, and dissociation energies. (C) 1999 American Institute of Physics. [S0021-9606(99)30708-X].