A Voronoi polyhedra analysis of structures of liquid water

Molecular dynamics simulations have been carried out for sinple point charge (SPC) water, in normal, compressed, and stretched states. A detailed analysis of local structures using both pair correlation and Voronoi polyhedra distribution, which describes the information about the multiparticle distribution, was reported. We examine the oxygen-oxygen pair correlation function and the distributions of Voronoi polyhedra in response to the variation of density and temperature. The asphericity distributions of Voronoi polyhedra reveals the anisotropicity of local arrangements of water molecules. It is found local pair distributions depend on the asphericities of center molecules. A high value of the asphericity parameter η corresponds to an icelike local structure of tetrahedrally bonded network patch. Loosely bonded structures, with low value of asphericity, have much less hydrogen bonding, and they are more susceptible to density fluctuation. Partition of local structures according to the asphericity of Voronoi polyhedra gives different pair correlation functions which give an identical set of isosbestic points. It is proposed that the Voronoi polyhedra analysis of configurations can be explained by a two-states patch model of water.