ACCURATE ATOMIC GAUSSIAN-BASIS FUNCTIONS FOR 2ND-ROW ATOMS - SMALL SPLIT-VALENCE 3-21SP AND 4-22SP BASIS-SETS

Small split-valence Gaussian 3-21SP and 4-22SP basis sets, previously reported for the first-row atoms [Chem. Phys. Lett., 229, 151 (1996)], have been extended for the second-row elements of the Periodic Table. The total energies of the ground states of the second-row atoms calcu lated with the new basis sets are significantly lower than those obtai ned with the well-known 3-21G (J. Am. Chem. Sec., 104, 2797 (1982)] an d 4-31G [J. Chem. Phys., 56, 5255 (1972)] basis sets. This is because, as first noted in our previous work for first-row atoms, that the 3-2 1G and 4-31G basis sets only correspond to a local minimum of the Hart ree-Fock energy functional, which is relatively far from its global mi nimum. The proposed basis sets have been tested by performing geometry optimizations and calculations of normal frequencies in the harmonic approximation of some diatomic and polyatomic molecules at the Hartree -Fock level. (C) 1997 by John Wiley & Sons, Inc.