Gaussian basis functions for use in molecular calculations. Contraction of (12s9p) atomic basis sets for the second row atoms

The contraction of the (12s9p) primitive basis sets of Veillard for the second row atoms is investigated. Contracted [7s], [6s], [5p], and [4p] basis sets are proposed. The [6s4p] contracted set gives a hartree-fock energy of -459.470g au for the ground state of the chlorine atom. This is a substantial improvement over results previously reported for contracted gaussian basis sets, even those obtained with much larger primitive sets.