Structure and Dynamics of Liquids Investigated by Quantum Beam: Binary Solution, Solution Under High Pressure, and Confined Solution

Abstract

Information on the structure and dynamics of liquids is necessary for understanding the properties and chemical reactivities of liquids at the molecular level. The structure and dynamics of liquids are clarified through quantum beam (X-ray and neutron) scattering experiments, which can be compared with data obtained from theoretical calculations (e.g., MD simulation, MC, RISM). The elastic scattering can clarify the static structure, and the quasi-elastic and inelastic scattering can clarify the translational and rotational motions and intramolecular and intermolecular vibrations depending on the energy resolution of the instruments. A high flux beam produced by synchrotron radiation and a pulsed neutron facility can reduce the sample size and measurement time. Therefore, a structural analysis of a liquid becomes possible under extreme conditions (high pressure and temperate and confinement within in a nanospace). Under such extreme conditions, these liquids have different properties and chemical reactivities compared with those in bulk. By compression, the tetrahedral-like structure of water is bent and transformed into the simple liquid-like structure. Although water confined in the mesospace does not freeze, the tetrahedral-like structure of confined water is developed with decreasing temperature. The temperature dependence of water dynamics follows the Vogel–Tammann–Fulcher (VTF) equation, where the relaxation time of molecular motion diverges at the ideal glass temperature. In this chapter, recent studies on the structure and dynamics of liquid molecules in binary solutions, at high temperature and high pressure, and in a confined environment are reviewed.