Relativistic Gaussian basis sets obtained with a polynomial version of the generator coordinate Dirac-Fock method: Ionization energies of some closed-shell atomic systems

Abstract

The purpose of this work is to analyze the relativistic Gaussian basis sets obtained with a recently developed polynomial version of the generator coordinate Dirac-Fock method. The atomic systems chosen to evaluate the basis sets are some alkaline earth and noble gas atoms: He, Be, Ne, Mg, Ar, and Ca. Hartree-Fock, relativistic, and electronic correlation contributions to the atomic total energy of the neutral and ionized atomic species were estimated using these relativistic Gaussian basis sets. The basis sets developed were able to attain energies that deviate at most by 0.47 and 0.65 mHartree, respectively, from numerical Hartree-Fock and Dirac-Fock-Coulomb results and are also competitive with fully optimized relativistic Gaussian basis sets of similar sizes. The electronic correlation energy contributions were obtained after two nonrelativistic calculations: a Hartree-Fock and a full quadratic configuration interaction, including single and double substitutions. The uncontracted basis sets obtained here along with polarization functions chosen to have equal exponents to selected functions already present in the original set were adequate in describing not only the neutral but also the highly ionized atomic species. The comparison of some calculated shell ionization energies with experimental results presented a maximum deviation of 3% (for a total of 15 ionization values ranging from 18 to 10,599 eV), reinforcing the quality of the basis sets developed in this work. © 2005 Wiley Periodicals, Inc.