Surprising properties of water on its binodal as the reflection of the specificity of intermolecular interactions

Abstract

In the paper the behavior of density (or specific volume), the heat of evaporation and entropy per molecule for normal and heavy water on their coexistence curves is discussed. The special attention is paid on the physical nature of the similarity in the behavior of density and the heat of evaporation for water and argon as well as the nearest water homolog $H_{2} S$. It is shown that the appearance of this similarity is a consequence of the rotational motion of water molecules, which averages the inter-particle potential in water and leads it to the argon-like form. To describe the fine distinctions in the behavior of the binodals for water and argon the dependence of the proper molecular volume on pressure is taken into account. In accordance with this often used the van der Waals and Carnahan-Starling equations of states are modified. The very surprising behavior of the entropy diameter for water is analyzed. It is shown that the nontrivial details of the temperature dependence for the entropy diameter is directly connected with the peculiarities of the rotational motion of molecules in water. The effect of strong dimerization of water molecules in the fluctuation region near the critical point is studied in details. The inner rotation of monomers forming the dimer $(D_{2} O)_{2} $ near the critical point is discovered.