Manifestation of cluster excitations in dielectric properties of water vapor and liquid water as well as their heat capacity

The main attention in this work is focused on the physical nature of the effective polarizability of water molecules in water vapor and liquid water. We will show that the main contribution to the effective polarizability of water vapor is formed by thermal vibration excitations of water dimers. At approaching the critical point this contribution becomes considerably greater than that caused by deformations of electron shells. In parallel with this we also show that the specific increase of the heat capacity of water vapor is mainly caused by the intramolecular vibrations and vibration excitations of water dimers. We propose a new method for the determination of dimer concentration in water vapor. This approach is generalized for the description of effective polarizability for liquid water. It is assumed that water can be considered as an ensemble of tetramers and dimers in wide temperature interval of liquid states. We analyze peculiarities of their thermal excitations in dense surroundings and their contributions to the effective polarizability of molecules. There is concentration of dimers, arising because of disintegration of tetramers, calculated. (C) 2018 Elsevier B.V. All rights reserved.