DENSITY-MATRIX AVERAGED ATOMIC NATURAL ORBITAL (ANO) BASIS-SETS FOR CORRELATED MOLECULAR WAVE-FUNCTIONS .1. 1ST ROW ATOMS

Generally contracted basis sets for first row atoms 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 several atomic states, positive and negative ions, and atoms in an external electric field. The contracted basis sets give virtually identical results as the corresponding uncontracted sets for the atomic properties, which they have been designed to reproduce. The design objective has been to describe the ionization potential, the electron affinity, and the polarizability as accurately as possible. The result is a set of well-balanced basis sets for molecular calculations. The starting primitive sets are 8 s4 p3 d for hydrogen, 9 s4 p3 d for helium, and 14 s9 p4 d3 f for the heavier first row atoms. © 1990 Springer-Verlag.