Supercritical Water: Density-Independent Angular Jumps.

Molecular dynamics simulations were employed to investigate the reorientation dynamics of water molecules under supercritical conditions. Our findings indicate that supercritical water consists of a fluctuating assembly of water clusters of varying sizes. The reorientational motions are characterized by large angular displacements and occur on fast time scales. We found that the decreasing density of supercritical water correlates with a decrease in the number of angular jumps as more water molecules were found in isolated or small clustered states at lower densities. Notably, the amplitude of rotational jumps in relative coordinates does not depend much on the density of supercritical water at a given temperature.