Faraday research article. Structural and dynamical aspects of aqueous ionic solutions

Abstract

The recently developed methods of neutron diffraction and isotopic substitution (NDIS) are shown to reveal structural details at higher than ever resolution, and provide insight into the origins of macroscopic properties of aqueous solutions. Moreover, these structural properties as defined through pair radial distribution functions, g(r), offer critical and substantial tests of computer simulation and theory at the atomic level.

The complementary technique of neutron quasielastic scattering (NQS) is used to determine the ‘scattering law’ for protons in solution. This property provides information on the dynamics of the water molecules, and can distinguish between cations whose hydration sphere is long, intermediate, or short-lived on a timescale of 5 × 10^–9τ_b/s 10^–10.

The power of both methods is illustrated by reference to a few examples, some of which relate to experiments only recently undertaken and the results of which will be published in the near future. The fact that these methods can be easily generalised has implications for many aspects of scientific endeavour where the focus of interest is a detailed understanding of the microstructural and dynamical properties of a liquid or amorphous system.