Connecting Density Functional Theory and Green's Function Theory
Weitao Yang, Ph.D, Advisor
Abstract: In past decades, theoretical and computational chemistry has been widely used to calculate chemical properties of different systems ranging from molecules to solid materials. It plays a critical role in understanding the existing systems and guiding new developments in chemistry, biochemistry and material science. Therefore, it is highly important to develop accurate and efficient theoretical approaches to provide insights into various phenomenon. The main workhouse in the electronic structure theory, density functional theory (DFT), has been successfully applied to calculate ground state and excited state properties for a broad range of systems. However, DFT fails to describe properties because of its intrinsic errors. The Green's function theory has gained increased attention in the past decade. It is highly accurate but its application is limited by the computational cost. In past few years, I have developed several approaches to predict both ground state and excited state properties of molecular systems including the renormalized singles Green's function approaches for predicting accurate ionization potentials and core-level binding energies, Bethe-Salpeter equation with localized orbital scaling correction for predicting accurate vertical excitation energies and multireference DFT with renormalized singles approach for describing strongly correlated systems. These approaches have a good balance between the accuracy and the computational cost, which make theoretical chemistry a robust and reliable tool for understanding the world.