PNNL

Abstract

Classical molecular dynamics simulations with polarizable potential models were carried out to quantitatively determine the effects of KCl salt concentrations on the electrostatic surface potentials of the vapor-liquid interface of water. To the best of our knowledge, the present work is the first calculation of the aqueous electrolyte surface potentials. Results showed that increased salt concentration enhanced the electrostatic surface potentials, in agreement with the corresponding experimental measurements. Furthermore, the decomposition of the potential drop into static charges and induced dipoles showed a very strong effect on the potential drop (an increase of ~1V per 1M) due to the double layers formed by KCl. However, this was mostly negated by the negative contribution from induced dipoles, resulting in a relatively small overall increase (~0.05V per 1M) in potential drop with increased salt concentration. This work was supported by the Office of Basic Energy Sciences of the Department of Energy, in part by the Chemical Sciences program and in part by the Engineering and Geosciences Division. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy. The funding of the Center for Biomolecules and Complex Molecular Systems is provided by the Ministry of Education of the Czech Republic under the project number LC512. The work performed at the Institute of Organic Chemistry and Biochemistry of the Academy of Sciences of the Czech Republic was a part of the research project Z40550506 and via the NSF-funded Environmental Molecular Science Institute (grants CHE 0431512 and 0209719) is gratefully acknowledged.