Beschreibung:
<jats:p>A structural study of TIP4P [W. L. Jorgensen et al., J. Chem. Phys. 79, 926 (1983)] water is presented. The method of structural analysis is based on the choice of restricted ranges of the pair angular configuration space. Such ranges, referred to as states or configurations Γ, are used to obtain restricted averages, gΓ(r), of the angular correlation function g(r,ω1,ω2). Eulerian angles are used to define molecular orientations. This allows one to analyze all the geometries of the configuration space and to pay due attention to the nonhydrogen bonded configurations. The local structures and their temperature evolution are studied using the restricted distribution functions of oxygen–oxygen, gOOΓ(r), and of oxygen–hydrogen gOHΓ(r) of the different configurations. As the temperature rises, the local population of nonhydrogen bonded configurations increases owing to the breakdown of the tetrahedral network. By comparing the gOOΓ(r) to the g(r) of simple fluids, scaled from liquid argon, the evidence of a residual tetrahedral network in liquid water at high temperature is obtained. Some restricted averages gOOΓ(r) reveal the existence of long-range direct correlation, masked by the orientational averages of the total distribution function gOO(r). The comparison between gOOΓ(r), evaluated at the liquid density and in the limit of zero density, shows that the direct correlation extends beyond four molecular diameters (about 12 Å for water) as in simple polar liquids. Finally, the dimer geometries contributing to form the first peak in gOHΓ(r) are identified. A practical method for determining the coordination numbers of hydrogen and nonhydrogen bonded molecules from the experimental data is suggested. Applied to TIP4P liquid water at various temperatures, the method yields coordination numbers in agreement with the random network model predictions.</jats:p>