QUALITY OF CORRELATING FUNCTIONS GENERATED FROM COMMONLY USED BASIS-SETS

Tests have been performed on the quality of correlating functions gene rated from commonly used Gaussian basis sets, such as the 4-31G and MI DI-4 sets. The atoms tested were carbon, nitrogen, and oxygen. Self-co nsistent field and configuration interaction (CI) calculations were pe rformed for the ground and lower excited states of neutral atoms as we ll as for positive and negative ions, using the original sets. Next, a fter adding (1) one d, and (2) two d and one f primitive Gaussian-type functions (GTFs) to the original sets, the CI calculations were repea ted. In order to investitgate the quality of the correlating orbitals generated from the GTF sets, parallel calculations to those for the GT F sets were carried out with an extended-set of Slater-type functions. It was found that the excitation energies change in a stepwise manner as the basis sets changed from the original sets to the original set +1d and the original set +2d1f. The Improvements in excitation energie s and ionization energies were almost independent of the original sets and were found to be strongly dependent on the augmented correlation functions. (C) 1996 by John Wiley & Sons, Inc.