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

Abstract

Molecular polarization at aqueous interfaces involves fast degrees of freedom that are often averaged-out in atomistic-modeling approaches. The resulting effective interactions depend on a specific environment, making explicit account of molecular polarizability particularly important in solutions with pronounced anisotropic perturbations, including solid/liquid interfaces and external fields. Our work concerns polarizability effects in nanoscale confinements under electric field, open to an unperturbed bulk environment. We model aqueous molecules and ions in hydrophobic pores using the Gaussian-charge-on-spring BK3-AH representation. This involves nontrivial methodology developments in expanded ensemble Monte Carlo simulations for open systems with long-ranged multibody interactions and necessitates further improvements for efficient modeling of polarizable ions. Structural differences between fixed-charge and polarizable models were captured in molecular dynamics simulations for a set of closed systems. Our open ensemble results with the BK3 model in neat-aqueous systems capture the ∼10% reduction of molecular dipoles within the surface layer near the hydrophobic pore walls in analogy to reported quantum mechanical calculations at water/vapor interfaces. The polarizability affects the interfacial dielectric behavior and weakens the electric-field dependence of water absorption at pragmatically relevant porosities. We observe moderate changes in thermodynamic properties and atom and charged-site spatial distributions; the Gaussian distribution of mobile charges onmore » water and ions in the polarizable model shifts the density amplitudes and blurs the charge-layering effects associated with increased ion absorption. The use of polarizable force field indicates an enhanced response of interfacial ion distributions to applied electric field, a feature potentially important for in silico modeling of electric double layer capacitors.« less

Authors:

Moučka, F.  ^[1];

• Search DOE PAGES for author "Moučka, F."
• Search DOE PAGES for ORCID "0000-0002-1400-7890"

Zamfir, S. ^[2]; Bratko, D.  ^[2];

• Search DOE PAGES for author "Bratko, D."
• Search DOE PAGES for ORCID "0000-0002-3675-5275"

Luzar, A.  ^[2]

• Search DOE PAGES for author "Luzar, A."
• Search DOE PAGES for ORCID "0000-0003-1640-191X"

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+ Show Author Affiliations

1. Virginia Commonwealth Univ., Richmond, VA (United States); J.E. Purkyne Univ. (Czech Republic)
2. Virginia Commonwealth Univ., Richmond, VA (United States)

Publication Date:

Wed Apr 24 00:00:00 EDT 2019

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division

OSTI Identifier:

1528912

Alternate Identifier(s):

OSTI ID: 1508683

Grant/Contract Number:  

SC0004406; AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 150; Journal Issue: 16; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 97 MATHEMATICS AND COMPUTING