Effect of Dipole Asymmetry on the Interfacial Behavior of Polar Fluids

Recent research using first-principles molecular dynamics has shown that water, despite being a neutral molecule, can generate a strong electric field at the air-water interface. We postulate that this anomalous interfacial behavior, which can catalyze atmospheric reactions, arises from dipole asymmetry, where the molecular center of mass is offset from its net dipole vector. Our study generalizes this idea, focusing on the underlying mechanisms for strong polarization and ion adsorption at the vapor--liquid interfaces of polar fluids. We find that asymmetry in molecular dipoles results in preferred orientations at the interface, leading to a finite electrostatic potential and stronger electric fields. Higher dipole moments increase fluid density and structural organization, while greater dipole offset asymmetry produces more distinct alignment and stronger electric fields at the interface. These results contribute to an improved understanding of interfacial polarization and offer potential applications in predictive climate change models.