Computer simulations of structural properties ofdiluite aqueous solutionsof rare gases from ambient to supercritical conditions

The properties of hydration of apolar solutes have become of large interest for the applications in many chemical processes in industrial technology and biochemistry. Computer simulation studies on aqueous solutions of rare gases indicate that at ambient conditions the solvation is governed by the formation of hydration cages around the solute. On raising temperature the solute tends to disrupt the cage. Recent neutron diffraction studies performed at supercritical conditions in mixtures of water and rare gases found that the structure of water is compressed by the presence of the solutes. The solubility of rare gases shows a very interesting temperature dependence: it presents a minimum between room temperature and the water boiling point, then it increases with raising temperature and more steeply above the water critical point. It has also been observed that the solubility of rare gases is larger for larger size of the solute. In this paper we study with computer simulation the structure of mixtures of Ar and water from ambient to supercritical conditions and we present a comparison of the pair correlation functions of these mixtures at supercritical conditions with recent experimental data. Results about the solubility of Ar and Ne in water are also shown and discussed. In the numerical calculations water is simulated with the SPC/E potential and the polarizable model developed by Brodholt, Sampoli and Vallauri (BSV).