Spatial distribution of ionic hydration energy and hyper-mobile water

Abstract

In this chapter, we provide the following two topics. 1: 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. 2: 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.