In liquids, the timescales for structure, diffusion, and phonon are all similar, of the order of a pico-second. This not only makes characterization of liquid dynamics difficult but also renders it highly questionable to describe liquids in these terms. In particular, the current definition of the structure of liquids by the instantaneous structure may need to be expanded because the liquid structure is inherently dynamic. Here, we advocate describing the liquid structure through the distinct-part of the Van Hove function, which can be determined by inelastic neutron and x-ray scattering measurements as well as by simulation. It depicts the dynamic correlation between atoms in space and time, starting with the instantaneous correlation function at t = 0. The observed Van Hove functions show that the atomic dynamics is strongly correlated in some liquids, such as water. The effect of atomic correlation on various transport properties of fluid, including viscosity and diffusivity, is discussed.

中文翻译：

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真实时空中液体中的相关原子动力学

在液体中，结构，扩散和声子的时标都相似，大约为皮秒。这不仅使液体动力学的表征变得困难，而且使得用这些术语描述液体非常成问题。特别地，由于液体结构固有地是动态的，因此可能需要扩大瞬时结构对液体结构的当前定义。在这里，我们主张通过范霍夫函数的不同部分来描述液体结构，这可以通过非弹性中子和X射线散射测量以及通过模拟来确定。它描述了原子在空间和时间之间的动态相关性，从t的瞬时相关函数开始=0。观察到的Van Hove函数表明，原子动力学在某些液体（如水）中具有很强的相关性。讨论了原子相关性对流体的各种传输特性（包括粘度和扩散率）的影响。