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arXiv · 2008.06811

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

Peihao Sun·J. B. Hastings·Daisuke Ishikawa·Alfred Q. R. Baron·Giulio Monaco
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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.

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Peihao Sun, J. B. Hastings, Daisuke Ishikawa, Alfred Q. R. Baron, Giulio Monaco. 2020-08-15. Two-component dynamics and the liquid-like to gas-like crossover in supercritical water. https://doi.org/10.1103/physrevlett.125.256001

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