X-ray scattering in liquid water at pressures of up to 7.7 kbar: Test of a fluctuation model

The pair correlation functions g(r) of liquid water obtained at pressures of up to 7.7 kbar at a constant temperature of 20 °C are discussed. A variety of evidence of the very strong effect of pressure on the structure of liquid water has been found. In particular, an unusual pressure dependence of the shortest intermolecular separation was observed. The results are interpreted in terms of fluctuations of the nearest environment, assuming that some of the structural configurations arising may be distinguished as preferred ones. The SIMPLEX procedure has been used to fit g(r) to the sum of correlation functions corresponding to the heavily destroyed structures of the solid phases of water. The results correlate with the phase diagram for water fairly well. This gives rise to an idea that water may be a suitable object for understanding the very nature of the liquid state.