Molecular Dynamics Study on the Density Fluctuation of Supercritical Water.

Abstract

A molecular dynamics simulation of the supercritical water was performed on a wide range of temperature and pressure near and above the critical point. Density fluctuations along the critical isochore line at 0.3 g cm-3 and some isobaric curves were calculated by the bin analysis method. The obtained values of the density fluctuation were plotted on a P-T phase diagram as contour lines. From this figure, it was found that the density fluctuation has a maximum at the critical point and ranging to a little higher temperature region. The ridge of the density fluctuation found by Nishikawa et al was also confirmed in this work and deviates from the critical isochore to lower density region with increasing pressure. It also found that the density fluctuation occurred not only near the critical point but in a rather wide T-P region of the supercritical state.