Molecular polarizabilities at aqueous interfaces, especially under the effect of an electric field, play a vital role in our understanding of energy storage devices such as electric double layer capacitors. Conventional atomistic force fields typically average out the effect of these polarizabilities, which can influence the outcome of a molecular simulation. Our work concerns non-trivial methodological developments of expanded ensemble Monte Carlo simulations for open systems with long-ranged multibody interactions. We consider both fixed-charge, SPC/E-JC, and polarizable, BK3-AH , models of water and ions in a hydrophobic pore which are subjected to an electric field. Molecular exchanges are allowed with an unperturbed bulk environment. Results with the BK3 water model in neat-aqueous systems capture the ∼10% reduction of molecular dipoles within the surface layer near the hydrophobic pore walls analogous to reported quantum mechanical calculations at water/vapor interfaces. Inclusion of polarizability affects the interfacial dielectric behavior and weakens the electric-field dependence of water absorption at pragmatically relevant porosities. Structural differences between fixed-charge and polarizable models were captured in Molecular Dynamics simulations for a set of closed systems. The use of polarizable force field indicates an enhanced response of interfacial ion distributions to applied electric field. Additionally, fixed-charge water experiences a more dramatic orientation-bias near the interface than its polarizable counterpart.

Molecular polarizability in open ensemble simulations of aqueous nanoconfinements under electric field

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.