Hydrogen bond network fluctuations

It is instructive to illustrate the use of Equations 5.19 and 5.29 using a simplistic 3-atom model calculation for water. Even though it is well established that the condensed phase structure of water is complicated and involves the coordinated motions of many molecules coupled through a constantly fluctuating hydrogen bond network, the fundamentals of the VPIE are represented reasonably well by the simplified model. 

CHARGE FLUCTUATIONS OF THE HYDROGEN BOND NETWORK AND PROTON TRANSFER ASSISTED BY THE SOLVENT IN PHENOL-WATER CLUSTERS... 

An aqueous system which is closely related to life is one of the most important eiqierimental systems. Water is regarded as a very unusual liquid. It has anomalous thermodynamic properties due to the existence of cavities and tetrahedrally-coordinated hydrogen bonds [52]. Water molecules may be considered as a continuum hydrogen-bonded network undergoing permanent topological rearrangement. This results in a fluctuating system which is affected by physicochemical and physical parameters e.g. pressure. 

This method of shape analysis applies also to other architectures. For instance, fluctuations in hydrogen-bonding networks play a key role in understanding solution properties. 3 Geometrical descriptors have been used to study these networks, including distribution of bonds and path connectivity in space.Overcrossing probabilities have been proposed as a tool for more detailed shape characterization,... 

The range of dynamic anomalies shown by liquid water at room temperature and pressure is truly amazing. It is not just the extended hydrogen-bond network that is responsible for this but also the small lifetime of an HB that allows large-scale fluctuations in liquid water (as discussed in Chapter 1). 

I. Ohmine and S. Saito,Water dynamics fluctuation, relaxation, and chemical reactions in hydrogen bond network rearrangement. Acc. Chem. Res., 32 (1999), 741. 

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