Temperature and pressure effects on the structure of liquid water

Structural studies of liquid water have been carried out for some time. However, no model has emerged that fully explains all the currently known features present. The radial-distribution function or the closely related pair-correlation function, used as interpretive tools for local structure, are known to be both pressure and temperature sensitive, indicating that: the local structure of liquid water changes as a function of these two variables. This would be expected. However, it is the details and subtleties of these structural changes that have not been understood. In this article, it is shown how non-hydrogen-bonded second neighbor considerations can be used to explain these structural changes. By use of an outer Structure two-state mixture model, which has been successful in explaining all the anomalies of water, the detailed,features of the structure functions and their sensitivity to temperature and pressure can be reproduced. In particular, the isochoric temperature differential X-ray scattering results of Bosio, Chen and Teixeira emerge from the analysis, giving new insights into the experiments. (C) 1999 Elsevier Science B.V. All rights reserved.