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Title: Molecular dynamics study of salt–solution interface: Solubility and surface charge of salt in water

The NaCl salt–solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt–solution interface system, and calculated the solubility of the salt using the direct method and free energy calculations, which are kinetic and thermodynamic approaches, respectively. The direct method calculation uses a salt–solution combined system. When the system is equilibrated, the concentration in the solution area is the solubility. In the free energy calculation, we separately calculate the chemical potential of NaCl in two systems, the solid and the solution, using thermodynamic integration with MD simulations. When the chemical potential of NaCl in the solution phase is equal to the chemical potential of the solid phase, the concentration of the solution system is the solubility. The advantage of using two different methods is that the computational methods can be mutually verified. We found that a relatively good estimate of the solubility of the system can be obtained through comparison of the two methods. Furthermore, we found using microsecond time-scale MD simulations that the positively charged NaCl surface was inducedmore » by a combination of a sodium-rich surface and the orientation of the interfacial water molecules.« less
Authors:
; ;  [1] ;  [2]
  1. Environment and Resource System Engineering, Kyoto University, Kyoto 615-8540 (Japan)
  2. Department of Energy and Hydrocarbon Chemistry, Kyoto University, Kyoto 615-8510 (Japan)
Publication Date:
OSTI Identifier:
22253179
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CRYSTALS; ELECTROPHORESIS; FREE ENERGY; INTERFACES; MOLECULAR DYNAMICS METHOD; SIMULATION; SODIUM CHLORIDES; SOLIDS; SOLUBILITY; SOLUTIONS; SURFACES