Structural Disorder in Supercritical Aqueous Ionic Solutions as seen by MD-EXAFS

Abstract

Because of their inherent structural disorder, liquids are challenging systems for structural studies. This is even more so for high temperature/high pressure fluids such as supercritical (SC) ones. By combining Molecular Dynamics simulations with Extended X-ray Absorption Fine Structure spectroscopy, we have recently elucidated the structure of the Br m hydration shell in low concentrated solutions from ambient to supercritical conditions [1]. The densities explored correspond to pressures up to 450 bar. In this paper, we show that this combination of techniques has been an essential tool to correctly interpret the experimental signals. Indeed, the occurrence of drastic different local environment of the ions in solutions, typical of liquids and magnified in supercritical conditions, can be seriously misleading if not taken into account.