Density oscillations in a model of water and other similar liquids

TL;DR

This paper proposes a model of water as a two-species ionic plasma with density oscillations, explaining sound anomalies and deriving eigenmodes, with potential applications to similar liquids and thermodynamic properties.

Contribution

It introduces a novel ionic plasma model for water's dynamics, deriving eigenmodes and dielectric functions, and generalizes to complex interactions and multi-component systems.

Findings

Eigenmodes of density oscillations derived for the ionic plasma model

Sound anomaly in water explained by the model

Structure factor calculated for generalized interactions

Abstract

It is suggested that the dynamics of liquid water has a component consisting of O^{-2z} (oxygen) anions and H^{+z} (hydrogen) cations, where z is a (small) reduced effective electron charge. Such a model may apply to other similar liquids. The eigenmodes of density oscillations are derived for such a two-species ionic plasma, included the sound waves, and the dielectric function is calculated. The plasmons may contribute to the elementary excitations in a model introduced recently for the thermodynamics of liquids. It is shown that the sound anomaly in water can be understood on the basis of this model. The results are generalized to an asymmetric short-range interaction between the ionic species as well as to a multi-component plasma, and the structure factor is calculated.