Ideality contours and thermodynamic regularities in supercritical molecular fluids

• DOI: 10.1016/j.cplett.2016.06.021
• Publication Date: 2016-06-11T12:04:43Z
• Authors: Caroline Desgranges; Abigail Margo; Jerome Delhommelle
• Keywords: 0103 physical sciences; 01 natural sciences; 7. Clean energy

Abstract Using Expanded Wang-Landau simulations, we calculate the ideality contours for 3 molecular fluids (SF 6 , CO 2 and H 2 O). We analyze how the increase in polarity, and thus, in the strength of the intermolecular interactions, impacts the contours and thermodynamic regularities. This effect results in the increase in the Boyle and H parameters, that underlie the Zeno line and the curve of ideal enthalpy. Furthermore, a detailed analysis reveals that dipole–dipole interactions lead to much larger enthalpic contributions to the Gibbs free energy. This accounts for the much higher temperatures and pressures that are necessary for supercritical H 2 O to achieve ideal-like thermodynamic properties.