Relativistic Calculations for Atoms, Molecules and Ionic Solids: Fully Ab-Initio Calculations and the Foundations of Pseudo-Potential and Perturbation Theory Methods

Abstract

It need hardly be pointed out at this conference that there is currently much interest in elucidating the role played by relativity in determining the electronic structure of atoms, molecules and solids. The subject of my two talks is the behaviour of the valence electrons in both atoms and molecules because the chemical properties of an element as well as the low frequency region of its electronic spectrum are essentially determined by these electrons. Thus the core electrons are only of interest in as far as they influence the behaviour of the valence electrons. There is evidence (eg. the appendix of |1|) that the purely quantum electrodynamic (QED) effects of Lamb shift and vacuum polarization, although important for core electrons |2|, are negligible for valence electrons. Consequently, these talks will be concerned solely with relativistic effects, defined as those contained with the Dirac equation and its many electron generalization (the Brown Hamiltonian including the Breit interaction), and will not consider the ‘one-body’ QED Lamb shift and vacuum polarization effects. The relativistic Dirac-Fock and non-relativistic Hartree-Fock Koopmans therem predictions of atomic ionization potentials shown in Table 1 provide ample evidence for the importance of relativistic effects in the valence shells of heavy atoms.