Effect of Dipole Asymmetry on the Interfacial and Bulk Behavior of Polar Fluids

Recent research in first-principles molecular dynamics has shown that water, though electrically neutral, generates an electric field strong enough to catalyze atmospheric reactions at the air-water interface. We propose that this anomalous behavior arises from dipole asymmetry, where the center of geometry of a molecule is offset from its center of dipole. Our study generalizes this idea by exploring the mechanisms of strong polarization and electric field generation at vapor-liquid interfaces of polar fluids. We find that introducing molecular dipole asymmetry into a shifted Stockmayer model leads to preferential orientation at the interface, resulting in a finite electrostatic potential. Higher dipole moments increase fluid density and structural organization at the interface. In addition, increasing dipole strength and offset in bulk liquid systems causes strong parallel alignment of dipole vectors at shorter radial distances. These findings further our understanding of polar liquid structure and interfacial polarization, with potential applications in climate chemistry.