Supercritical water: relationships of certain measured properties to the extent of hydrogen bonding obtained from a semi-empirical model

Abstract

A mixture model is applied to supercritical water, recognizing as species non-, singly-, and doubly- (or more) hydrogen bonded water molecules. The model is able to describe adequately the density within the tested range 660 to 880 K and 35 to 100 MPa. The model parameters, obtained from fitting the density, yield the extent of hydrogen bonding in terms of the fractions of the species present. These are then employed to describe the heat capacity at constant volume, the self-diffusion coefficient at the lower temperature of this range, the Kirkwood dipole orientation correlation coefficient, the NMR chemical shifts, and the IR integrated absorption of the OD or OH bands over the conditions where data exist.