Kryuchkov Nikita P, Mistryukova Lukiya A, Brazhkin Vadim V, Yurchenko Stanislav O
Bauman Moscow State Technical University, 2nd Baumanskaya street 5, Moscow, 105005, Russia.
Institute for High Pressure Physics RAS, Kaluzhskoe shosse, 14, Troitsk, Moscow, 108840, Russia.
Sci Rep. 2019 Jul 19;9(1):10483. doi: 10.1038/s41598-019-46979-y.
Although the understanding of excitation spectra in fluids is of great importance, it is still unclear how different methods of spectral analysis agree with each other and which of them is suitable in a wide range of parameters. Here, we show that the problem can be solved using a two-oscillator model to analyze total velocity current spectra, while other considered methods, including analysis of the spectral maxima and single mode analysis, yield rough results and become unsuitable at high temperatures and wavenumbers. To prove this, we perform molecular dynamics (MD) simulations and calculate excitation spectra in Lennard-Jones and inverse-power-law fluids at different temperatures, both in 3D and 2D cases. Then, we analyze relations between thermodynamic and dynamic features of fluids at (Frenkel) crossover from a liquid- to gas-like state and find that they agree with each other in the 3D case and strongly disagree in 2D systems due to enhanced anharmonicity effects. The results provide a significant advance in methods for detail analysis of collective fluid dynamics spanning fields from soft condensed matter to strongly coupled plasmas.
尽管对流体中激发光谱的理解非常重要，但目前仍不清楚不同的光谱分析方法之间如何相互吻合，以及哪种方法在广泛的参数范围内适用。在此，我们表明可以使用双振子模型来分析总速度电流光谱以解决该问题，而其他考虑的方法，包括光谱最大值分析和单模分析，会得出粗略的结果，并且在高温和高波数下变得不适用。为了证明这一点，我们进行了分子动力学（MD）模拟，并计算了三维和二维情况下不同温度下 Lennard-Jones 流体和逆幂律流体中的激发光谱。然后，我们分析了流体在从液态到气态的（弗伦克尔）转变过程中的热力学和动力学特征之间的关系，发现它们在三维情况下相互吻合，而在二维系统中由于增强的非谐效应而强烈不一致。这些结果在从软凝聚态物质到强耦合等离子体的集体流体动力学详细分析方法方面取得了重大进展。
