Browsing by Author "Stamper, C"

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    Experimental confirmation of the universal law for the vibrational density of states of liquids
    (American Chemical Society, 2022-04-02) Stamper, C; Cortie, DL; Yue, ZJ; Wang, XL; Yu, DH
    An analytical model describing the vibrational density of states (VDOS) of liquids has long been elusive, owing to the complexities of liquid dynamics. Nevertheless, Zaccone and Baggioli have recently developed such a model which was proposed to be the universal law for the vibrational density of states of liquids. Distinct from the Debye law, g(ω) ∝ ω2, for solids, the universal law for liquids reveals a linear relationship, g(ω) ∝ ω, in the low-energy region. We have confirmed this universal law with experimental VDOS measured by inelastic neutron scattering on real liquid systems including water, liquid metal, and polymer liquids, and have applied this model to extract the effective relaxation rate for the short time dynamics for each liquid. The model has also been further evaluated in the prediction of the specific heat with comparison to existing experimental data as well as with values obtained by different approaches. © 2022 American Chemical Society
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    On the temperature dependence of the density of states of liquids at low energies
    (Springer Nature, 2024-08-13) Jin, S; Fan, X; Stamper, C; Mole, RA; Yu, Y; Yu, DH; Baggioli, B; Hong, L
    We report neutron-scattering measurements of the density of states (DOS) of water and liquid Fomblin in a wide range of temperatures. In the liquid phase, we confirm the presence of a universal low-energy linear scaling of the experimental DOS as a function of the frequency, g(w) = a(T)w , which persists at all temperatures. The low-frequency scaling of the DOS exhibits a sharp jump at the melting point of water, below which the standard Debye’s law, g(w) ∝ w2 , is recovered. On the contrary, in Fomblin, we observe a continuous transition between the two exponents reflecting its glassy dynamics, which is confirmed by structure measurements. More importantly, in both systems, we find that the slope a(T) grows with temperature following an exponential Arrhenius-like form, a(T) ∝ exp(−/T) . We confirm this experimental trend using molecular dynamics simulations and show that the prediction of instantaneous normal mode (INM) theory for a(T) is in qualitative agreement with the experimental data. © The Authors - Open Access This article is licensed under a Creative Commons Attribution 4.0 International License.