  Molecular dynamics simulations of supercritical water reveal distinctly
different distance-dependent modulations of dipolar response and correlations
in particle motion compared to ambient conditions. The strongly perturbed
H-bond network of water at supercritical conditions allows for considerable
translational and rotational freedom of individual molecules. These changes
give rise to substantially different infrared spectra and vibrational density
of states at THz frequencies for densities above and below the Widom line that
separates percolating liquid-like and clustered gas-like supercritical water.
