Communication: Modeling of concentration dependent water diffusivity in ionic solutions: Role of intermolecular charge transfer

Journal Article · Mon Dec 28 00:00:00 EST 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4938083· OSTI ID:22493358

Yao, Yi; Kanai, Yosuke ^[1]

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1. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States)

The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na{sup +} and K{sup +} ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.

• OSTI ID: 22493358
• Journal Information: Journal of Chemical Physics, Vol. 143, Issue 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABUNDANCE
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CONCENTRATION RATIO
DIFFUSION
MANY-BODY PROBLEM
MOLECULAR DYNAMICS METHOD
MOLECULES
POTASSIUM CHLORIDES
POTASSIUM IONS
QUANTUM MECHANICS
SALTS
SODIUM CHLORIDES
SODIUM IONS
SOLUTIONS
WATER