Oxygen isotope fractionation in H2O and the structure of liquid water

摘要

The difference between the atomic force constant for oxygen in ice I and liquid water, and that in the vapor phase is determined from an analysis of H2thinsp;16O/H2thinsp;18O isotope fractionation factors. It is shown that the force constants in liquid water depend explicitly upon the hydrogenhyphen;bond distribution in the liquid phase, and upon fusion the average number of hydrogen bonds per H2O decreases from 4 to 3. This result and the number of hydrogen bonds in water above the ice point are compared with the numbers obtained from molecular dynamics calculations and the cluster and latticendash;gas theories of liquid water.