Abstract
Dynamic properties of supercritical water at temperatures between 573 and 773 K and densities between 0.49 and 0.83 have been investigated by molecular dynamics simulation and compared to states located on the vapor-liquid coexistence curve. A flexible simple point charge potential has been assumed for interactions in the subcritical states, whereas a reparameterization of that model has been performed to model the supercritical states. The hydrogen bonding structure and the diffusion coefficients in an ensemble of simulated states were previously analyzed and a good agreement with available experimental data was found. Dynamic properties of hydrogen bonding like the bond lifetimes and the influence of hydrogen bonds in the vibrational spectra are discussed along a range of simulation conditions. A nonlinear behavior of the hydrogen-bond lifetime as a function of temperature is observed in subcritical water whereas a linear dependence is found in supercritical water. Special attention is paid to the intermolecular vibrational spectrum (10–400 It has been observed that the mode centered at 200 attributed to the intermolecular O—O stretching vibration in the ambient state remains active in the supercritical states.
- Received 24 March 1999
DOI:https://doi.org/10.1103/PhysRevE.61.449
©2000 American Physical Society