Highly Accurate Molecular Properties using variational Quantum Electrodynamics

Objective

Quantum chemical calculations are today in a position where they not only assist, but may also challenge experiment, at least for molecules containing light atoms only. When heavy atoms are present, achieving the same accuracy becomes more challenging, not only because of relativistic effects, but also because the larger number of electrons and the often complicated electronic structures make the electron correlation problem harder. When surveying the physics that has to be included in order to establish a reliable computational protocol for heavy-element chemistry, the role of quantum electrodynamics (QED) should at least be considered. Studies so far indicate that QED-effects reduce relativistic effects by about 1%. However, such investigations have been mostly limited to valence properties, since there are currently no reliable tools for general molecules to study the core region where the QED-effects are generated. The HAMP-vQED project aims to fill this gap by providing a computational machinery allowing highly accurate calculations of molecular properties, with particular focus on properties that probe electron density in the core region, such as NMR parameters. I insist on a variational approach to QED using the local, finite basis sets of quantum chemistry. In short, I want to do QED without diagrams. This allows me to verify the domain of validity of currently used effective QED-potentials and provide a more consistent formulation of relativistic quantum mechanics. QED has been called the last train from physics to chemistry. The HAMP-vQED project provides a train back to physics in the form of highly accurate calculations which, combined with experiment, will allow the exploration of nuclear structure, the standard model of the universe and beyond. An even more tantalizing perspective is that such a variational scheme to QED may inspire progress in other quantum field theories, such as quantum chromodynamics, where perturbation theory is more problematic.