To understand intermolecular interactions and one-electron properties we are developing post-Kohn-Sham (KS) approaches. The focus is on random phase approximation (RPA)-based methods that seamlessly incorporate van der Waals interactions to all orders and incorporate screening effects. The latter is particularly important as we tackle charge transfer processes in the regimes of molecular materials and liquids. We have formulated a generalized Kohn-Sham (GKS) scheme for a semi-canonical projected (sp) RPA that provides accurate energy and potential based properties such as intermolecular interaction energies and principal ionization potentials. Our initial results have shown that anions are correctly predicted to be stable within the GKS-spRPA scheme, which is currently a limitation for several semi-local functionals. We have also shown that accurate core-electron binding energies can be simulated using GKS-spRPA without any need for core-hole references states. Our current focus in this area involves extension of GKS-spRPA methods for X-ray spectroscopy and developing efficient algorithms that enable large-scale GKS-spRPA computational studies.
Electronic Structure Method Development
