8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P2.64Tue 611:23-14:00The micro-structure of liquid waterAurélien Perera 11 Laboratoire de Physique Théorique de la Matière Condensée, Université Pierre et MarieCURIE, F75252, Paris, FranceThe microscopic structure of liquid water has been the subject of many speculations since the earlymodels proposed by Röngten and Franck. Liquid water has more than 60 anomalous properties andnone of the proposed models seem to describe all of them in a unified way. Instead of investigatingthese anomalies, we focus here on the natural statistical probe of the structure of liquids, the paircorrelation function. In the case of water, the 3 site-site distribution functions g HH, g OH and gOO can be obtained by various scattering experiments and model dependant computer simulations.We show that all the popular water models have very similar features: liquid correlations untilabout 10A, followed by an apparent extinction of correlations beyond this distance. We analysethe influence of the partial charges on this particular structure, by varying them from uncharged tofully charged, and we show how the particular structure of water sets in only from charging ratio9/10. The structure of the liquid evolves from that of an ordinary Lennard-Jones liquid correlatedover all distances to that of liquid water correlated only over a shell of radius 10A. This is possibleonly if water molecules form tight H-bonded clusters within this shell. Such clusters are notobserved in computer simulations. To reconciliate these apparently diverging observations, wepropose that these ”correlation clusters”(detected through correlation functions) are overlapping,hence non-interacting entities. The overlap occurs by switching of H-bond between moleculesbelonging to neighbouring such ”phantom clusters”. We also show that these entities are robustto mixing with various types of solutes, since the same type of structure is observed, even up toequimolar mixing conditions.64