A theoretical study of molecular positron binding based on a correlation-polarization potential approach combined...

We present an improved density functional theory with a correlation-polarization potential (DFT-CPP) for investigating positron binding in molecules. In the original DFT-CPP approach, the polarization potential is placed at the molecular center, which often leads to inaccurate descriptions of positron binding, particularly in large systems. To overcome this limitation, we develop a method that distributes the polarization potential over individual atoms by employing position-dependent electric susceptibilities within a dielectric-dependent DFT framework. This first-principles approach provides a physically grounded description of how each part of a molecule responds to an approaching positron, based directly on its electronic structure. We also compute and analyze positron affinities for normal alkanes, cyclic hydrocarbons, acenes, and siloxanes. Our results reproduce experimental data for alkanes, capture electron-positron response in cyclic hydrocarbons and acenes, which had previously been insufficiently described by polarizability alone, and extend the analysis to siloxanes, which have remained challenging for empirical methods.