ATOMIC FORCE CONSTANTS AND THE STRUCTURE OF LIQUID WATER

Abstract

The atomic force constants for oxygen atoms In Ice I, liquid water, and water vapor have been determined from the analysis of spectroscopic data on water vapor, and the $H_{2}O^{16}/H_{2}O^{18}$ isotope fractionation factors between the condensed and vapor phases. It is found that the atomic force constants In Liquid water can be expressed in terms of the force constants in ice and water vapor, and the hydrogen bond distribution in the liquid phase. The atomic force constants calculated using these results and the hydrogen bond distribution derived by Stillinger and $Rahman^{1}$ from the ``molecular dynamics” computer simulation of liquid water, are found to be in excellent agreement with experiment, whereas the force constants calculated using the hydrogen bond distributions given by some other models are not.