Charge-Dependent Basis Sets. I. First Row Elements

Abstract

The effects of the molecular environment on the atomic orbital (AO) exponents have been taken into account by varying them with the electronic population. The dependence of these AO exponents was described by a quadratic equation involving the net atomic charges or the individual AO populations. These AO exponents were allowed to vary within the range defined by the AO exponents of the cation and anion atomic species. The atomic charges and AO populations were calculated by the Mulliken and the Löwdin population analysis approaches. Several molecules (HCN, HNC, CH3F, CH3OH), molecular anions (OH-, NH2-, N3-, NO2-), and chemical reactions (HCN → HNC; F- + CH3OH → FCH3 + OH-) were used to test this charge-dependent approach for basis sets. Very significant differences were obtained for the anionic systems (molecules and transition states) when the charge-dependent and charge-independent basis sets were employed. © 1999 John Wiley & Sons, Inc.