Small Gaussian basis sets for molecular calculations. II. Effect of basis set size on the calculated wavefunction and a useful GTO basis set

Abstract

A quantitative assessment of the importance of basis set variation at the minimal basis level of accuracy has been carried out. A number of basis sets, using Gaussian lobe functions, were tested by calculating the energy and one-electron properties for a number of molecules and the results used to select an optimum sized accurate basis set. This basis set consisted of a five-component 1s-Gaussian type orbital (GTO), a three-component 2s-GTO and a three-component 2p-GTO for each first row atom, and a three-component 1s-GTO for hydrogen. The accuracy of wave functions calculated with the minimal basis sets was very sensitive to changes in the 2p-GTO.     A Gaussian lobe basis set of optimum size for use with large molecules is given. The results of testing this set by calculating several one-electron properties for ten molecules, together with confidence limits, are also presented.