DENSITY-MATRIX AVERAGED ATOMIC NATURAL ORBITAL (ANO) BASIS-SETS FOR CORRELATED MOLECULAR WAVE-FUNCTIONS .3. FIRST ROW TRANSITION-METAL ATOMS

Generally contracted basis sets for the first row transition metal ato ms Sc-Zn have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over the three electr onic configurations d(n), d(n-1)s, and d(n-2)s(2) for the neutral atom as well as the ground state for the cation and the ground state atom in an external electric field. The primitive sets are 21s15p10d6f4g. C ontraction to 6s5p4d3f2g yields results that are virtually identical t o those obtained with the corresponding uncontracted basis sets for th e atomic properties, which they have been designed to reproduce. Sligh tly larger deviations are obtained with the 5s4p3d2f1g for the polariz ability, while energetic properties still have only small errors. The design objective has been to describe the ionization potential, the po larizability and the valence spectrum as accurately as possible. The r esult is a set of well-balanced basis sets for molecular calculations, which can be used together with basis sets of the same quality for th e first and second row atoms.