Local Fermi Orbitals: From DFT Corrections to Molecular Charge Transfer

Local orbitals play a significant role in understanding chemical and material properties. They are widely used to probe electronic structure, particularly bonding interactions and to accelerate electronic structure calculations for large molecules by exploiting the sparsity afforded by their localized nature. In this talk, we will present approaches and results based on the local Fermi orbitals. First introduced by Luken, a Fermi orbital mimics the exchange hole surrounding an electron located at a chosen reference point, referred to as the descriptor position. The location of this descriptor position entirely determines the size and shape of a Fermi orbital.  Symmetric orthogonalization of the Fermi orbitals yield Fermi-Lowdin orbitals. We will describe our work on using the Fermi-Lowdin orbitals to mitigate self-interaction errors in density functional theory with applications to the electronic response of systems subjected to external electric fields and charge separation. In the second part of the talk, we will introduce an approach for describing electron transport through molecules using localized Fermi-Lowdin orbitals. Finally, we will present results on electron transfer between an organic donor and “forever chemical” molecules known as PFAS.