Two-component dynamics and the liquid-like to gas-like crossover in supercritical water

Abstract

Molecular-scale dynamics in sub- to super-critical water is studied with inelastic X-ray scattering and molecular dynamics simulations. The obtained longitudinal current correlation spectra can be decomposed into two main components: a low-frequency (LF), gas-like component and a high-frequency (HF) component arising from the O--O stretching mode between hydrogen-bonded molecules, reminiscent of the longitudinal acoustic mode in ambient water. With increasing temperature, the hydrogen-bond network diminishes and the spectral weight shifts from HF to LF, leading to a transition from liquid-like to gas-like dynamics with rapid changes around the Widom line.

7 pages, 4 figures

References in corpus (6)

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• Collective modes and thermodynamics of the liquid state
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Cited by in corpus (5)

• Elementary vibrational model for transport properties of dense fluids
• Note: Gas-liquid crossover in the Lennard-Jones system
• Transcritical transition of the fluid around the interface
• Structural effect on phonon attenuation in metallic liquids and glasses
• Universal two-component dynamics in supercritical fluids