Synergism of the dynamics of tetrahedral hydrogen bonds of liquid water

TL;DR

This study analyzes the temperature-dependent molecular dynamics of water, revealing a phase transition around 298 K driven by tetrahedral hydrogen bond fluctuations and their synergistic reactions.

Contribution

It introduces a modified Arrhenius approach to elucidate the role of hydrogen bond fluctuations in water's phase transition and dynamics.

Findings

Significant difference in water MD below and above 298 K.

Identification of a phase transition at 298 K involving tetrahedral HBs.

Hydrogen bond dipole fluctuations are key to water's dynamic behavior.

Abstract

We used modified Arrhenius approximations to analyze the known temperature dependences (TDs) of water microstructure parameters and its dynamic characteristics. The analysis of activation energies showed a significant difference in the molecular dynamics (MD) of water in the ranges from 273 to 298 K and from 300 to 373 K. The features of MD in the first range were associated with the metastable ice-like phase of water, in which hexagonal clusters with tetrahedral hydrogen bonds (HBs) predominate. Based on the ratios of the signs and values of the activation energies of HBs fluctuations and the parameters of the microstructure, it was assumed that fluctuations of HBs dipoles play a key role in the mechanism of resonant activation by thermal energy of consistent reactions of deformation, rupture and formation of tetrahedral HBs in water clusters. The synergism of these reactions and the interaction of the charges of the vacant acceptor and donor tetrahedral orbitals of the oxygen atom trigger at 298 K an explosive transition of the metastable ice like phase of water into the argon like phase. The synergetics of water dynamics above 298 K is adequately characterized by the product diffusion on viscosity, from which TDs follow the activation energies of reactions that determine the form of the Stokes Einstein relation in the temperature ranges below and above the 298 K point.