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Title: Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions

Abstract

Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for coarse grained models of electrolyte solution. Here, we provide rigorous definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation (DFT-MD) and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to highly unphysical values for the solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry (CHA) for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation. We would like to thank Thomas Beck, Shawn Kathmann, Richardmore » Remsing and John Weeks for helpful discussions. Computing resources were generously allocated by PNNL's Institutional Computing program. This research also used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. TTD, GKS, and CJM were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. MDB was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative, a Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated by Battelle for the U.S. Department of Energy.« less

Authors:
ORCiD logo [1];  [1];  [1];  [2]
  1. Physical Science Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA
  2. Department of Chemical Engineering, University of Washington, Seattle, Washington 98185, USA
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1422317
Report Number(s):
PNNL-SA-123710
Journal ID: ISSN 0021-9606; KC0301050
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 147; Journal Issue: 16
Country of Publication:
United States
Language:
English

Citation Formats

Duignan, Timothy T., Baer, Marcel D., Schenter, Gregory K., and Mundy, Chistopher J. Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions. United States: N. p., 2017. Web. doi:10.1063/1.4994912.
Duignan, Timothy T., Baer, Marcel D., Schenter, Gregory K., & Mundy, Chistopher J. Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions. United States. doi:10.1063/1.4994912.
Duignan, Timothy T., Baer, Marcel D., Schenter, Gregory K., and Mundy, Chistopher J. Sat . "Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions". United States. doi:10.1063/1.4994912.
@article{osti_1422317,
title = {Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions},
author = {Duignan, Timothy T. and Baer, Marcel D. and Schenter, Gregory K. and Mundy, Chistopher J.},
abstractNote = {Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for coarse grained models of electrolyte solution. Here, we provide rigorous definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation (DFT-MD) and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to highly unphysical values for the solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry (CHA) for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation. We would like to thank Thomas Beck, Shawn Kathmann, Richard Remsing and John Weeks for helpful discussions. Computing resources were generously allocated by PNNL's Institutional Computing program. This research also used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. TTD, GKS, and CJM were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. MDB was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative, a Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated by Battelle for the U.S. Department of Energy.},
doi = {10.1063/1.4994912},
journal = {Journal of Chemical Physics},
number = 16,
volume = 147,
place = {United States},
year = {Sat Oct 28 00:00:00 EDT 2017},
month = {Sat Oct 28 00:00:00 EDT 2017}
}