论文标题
液态水的非牛顿粘弹性行为的分子解释
Molecular interpretation of the non-Newtonian viscoelastic behavior of liquid water at high frequencies
论文作者
论文摘要
使用经典以及AB-Initio分子动力学模拟，我们计算了纯水和水甘油混合物的频率依赖性剪切粘度。与最近的实验一致，我们发现THZ政权中牛顿流体行为的偏差。基于麦克斯韦模型的扩展，我们引入了一个粘弹性模型，以描述观察到的纯水粘度光谱。我们在光谱中发现了四种弛豫模式，我们将其归因于i）氢键网络拓扑变化，ii）水对的氢键伸展振动，iii）水分子三重态的集体振动，以及iv）单个水分子的图库激发。我们的模型定量地描述了液态水在短时标准上的粘弹性响应，其中通过牛顿流体模型的流体动力描述分解。
Using classical as well as ab-initio molecular dynamics simulations, we calculate the frequency-dependent shear viscosity of pure water and water-glycerol mixtures. In agreement with recent experiments, we find deviations from Newtonian-fluid behavior in the THz regime. Based on an extension of the Maxwell model, we introduce a viscoelastic model to describe the observed viscosity spectrum of pure water. We find four relaxation modes in the spectrum which we attribute to i) hydrogen-bond network topology changes, ii) hydrogen-bond stretch vibrations of water pairs, iii) collective vibrations of water molecule triplets, and iv) librational excitations of individual water molecules. Our model quantitatively describes the viscoelastic response of liquid water on short timescales, where the hydrodynamic description via a Newtonian-fluid model breaks down.
