Spatial Distribution of Ionic Hydration Energy and Hyper-Mobile Water
We carry out DRS measurements for divalent metal chloride and trivalent metal chloride solutions and clarify the hydration states. All the tested solutions have hyper-mobile water (HMW) with higher dielectric relaxation frequency f1 (~20 GHz) than that of bulk water (12.6 GHz at 10 °C), and dispersion amplitude of HMW is aligned to Hofmeister series. According to the correlation between an intensity of HMW signal and water structure entropy, HMW can be a scale for the water structure.
We carry out the spatial-decomposition analysis of energetics of hydration for a series of ionic solutes in combination with molecular dynamics (MD) simulation. The hydration analysis is conducted on the basis of a spatial-decomposition formula for the excess partial molar energy of the ion that expresses the thermodynamic quantity as an integral over the whole space of the ion–water and water–water interactions conditioned by the ion–water distance. In addition, we examine the correlation between the electric field formed by ion and the number of HMW around ion.
KeywordsDielectric relaxation spectroscopy Hyper-mobile water Ionic hydration energy Spatial distribution Hofmeister effect
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