Incorporating Relativistic Effects in the Calculation of Core and Valence Excitations in Metal Complexes and Molecular Clusters

Abstract

Spectroscopy is one of the most powerful tools humanity has to probe the structure of matter. By seeing how light interacts with the atoms or molecules in a sample, intricate details of the quantum mechanical structure is revealed. Calculations of the quantum mechanical description of the electronic structure allows for both the prediction of observed phenomena, as well as an explanation of the physical processes underlying those observations. Although calculations that ignore corrections from special relativity are often sufficient, the inclusion of relativistic effects can be of great importance. Systems with heavy nuclei are especially well-known for strong corrections from relativity that are essential for even a qualitatively correct prediction. The work here focuses on including relativistic effects from first principles in electronic structure calculations to predict spectra of both core and valence excitations. In the first half, developments using the real-time approach of TDDFT with the X2C method are recounted, including the prediction of L-edge X-ray absorption spectra for transition metal complexes. The second half details developments using the frequency-based approach of TDDFT. This also entailed the development of new eigensolvers to more efficiently converge states in the high-energy region, as well as extensions of natural transition orbitals and visualization techniques for complex, two-component orbitals. Investigation of the Rashba effect in the valence excitations in ZnO semiconducting quantum dots conclude the work.