Atomic and Molecular Pseudopotential Studies Using Gaussian Orbitals

The Hellmann model potential is employed for the first time in atomic and molecular calculations with a Gaussian basis set. The use of Gaussian functions allows for the simple application of the pseudopotential method to large molecular systems while maintaining the accuracy exhibited by Slater-type-orbital calculations. A new model potential specifically designed for Gaussians, V(r) = C1r2 + C2, is proposed and used to examine a series of two-valence-electron atoms. A number of diatomic molecules are studied with both the Hellmann and Gaussian model potentials. Bond lengths, vibrational frequencies, dipole moments, and dissociation energies are calculated, and the results are generally in good accord with experimental data. The Phillips–Kleinmann pseudopotential formalism is used to examine the model potentials and analyze the atomic and molecular results.