Electrostatics of interfaces is fundamentally different from electrostatics of bulk materials. Electrostatic inhomogeneity extends deep into the bulk affecting charged and polar molecules in the interface. Observable properties such as absorption of radiation by solutions, optical spectroscopy of dyes, and dielectric spectroscopy of solutions connect the structure of the interface with observables measured in the laboratory. The extended nature of the aqueous interface is significant to cellular biology mostly operating in the interface.
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Interfacial Structural Transition in Hydration Shells of a Polarizable Solute
Electrostatics of polar solvation is typically described by harmonic free energy functionals. Polarizability contributes a negative polarization term that can make the harmonic free energy negative. The harmonic truncation fails in this regime. Simulations of polarizable ideal dipoles in water show that water’s susceptibility passes through a maximum in the range of polarizabilities zeroing the harmonic term out.