Why thermodynamic properties of normal and heavy water are similar to those of argon-like liquids?

The Letter is devoted to the explanation of the argon-like behavior of the thermodynamic properties of water. It is shown that this phenomenon is caused by the averaged inter-particle potentials which form due to rotation of water molecules. The general structure of the averaged potentials is proposed. The physical nature for the considerable shift of the triple point of water in comparison with the one obtained by extrapolation in the homological series is discussed.