ABSTRACT
Water exhibits many peculiar properties that are generally attributed to its hydrogen-bonded network structure.1,2 Some of these peculiar properties include negative volume of melting, density maximum, high dielectric constant, high mobility of protons and hydroxide ions, etc. It is also a ubiquitous solvent that easily dissolves ions under ambient conditions. However, water above its critical temperature (647 K) and pressure (22.1 MPa) behaves very differently from normal water.3-5 For example, unlike water under ambient conditions, supercritical water behaves more like a nonpolar solvent that prefers to dissolve organic solutes rather than ionic solutes. More importantly, the density of supercritical water can be tuned from liquidlike to gaslike densities without any liquid-gas phase transition, leading to huge changes in its solvation properties. The altered solvent properties of supercritical water are believed to arise from changes in the hydrogen bond characteristics of the solvent as one moves from ambient to supercritical conditions.
