Structural model of liquid water

Water is a unique substance in view of its unusual physical and chemical properties  

Many models for the structure of liquid water have been proposed. One of the most useful is the polyhedral model. 

In liquid water, the thermal motions of molecules are perpetual, and the relative positions of the molecules are changing all the time. Although the structure of liquid water has no definite pattern, the hydrogen bonds between molecules still exist in large numbers. Thus liquid water is a dynamic system in which the H2O molecules self-assemble in perfect, imperfect, isolated, linked and fused polyhedra (Fig. 16.3.3), among which the pentagonal dodecahedron takes precedence. 

The ideal process of the melting of ice may be visualized as a partial ( 15%) breakage of hydrogen bonds to form ice fragments, which are then converted into a polyhedral system, as indicated in Fig. 16.3.4. 

The polyhedral model is useful for understanding the properties of liquid water. 

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Dougherty, R. C., and L. N. Howard. 1998. Equilibrium structural model of liquid water evidence from heat capacity, spectra, density, and other properties. J. Chem. Phys. 109 7379-7393. 

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