Characterization of the Local Structure in Liquid Water by Various Order Parameters.
Characterization of the Local Structure in Liquid Water by Various Order Parameters.
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DOI：
10.1021/acs.jpcb.5b02936
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发表时间：
2015-07-02
期刊：
影响因子：
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通讯作者：
Laage D
中科院分区：
文献类型：
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作者：
Duboué-Dijon E;Laage D
已经提出了广泛的几何序参数来表征液态水的局部结构及其四面体排列，但它们各自的优点仍然难以捉摸。在这里，我们考虑了一系列流行的顺序参数和分析水的分子动力学模拟，在散装和水化壳的疏水溶质，在298和260 K。我们发现，这些参数是弱相关的，探测不同的失真，例如角与径向的障碍。我们首先联合收割机这些互补的描述，分析结构重排导致的密度最大的液态水。我们的研究结果表明，没有迹象表明一个不均匀的混合物，并表明，密度最大值产生的间隙水分子冷却时的耗尽。在丙醇的疏水部分的水化壳层中，有序参数表明水的局部结构与本体中的结构相似，在有序构型中仅具有非常弱的耗尽，从而证实不存在任何冰山型结构。最后，我们表明影响本体中水重取向动力学的主要结构波动是角度扭曲，我们用跳跃氢键交换机制解释了这一点。
A wide range of geometric order parameters have been suggested to characterize the local structure of liquid water and its tetrahedral arrangement, but their respective merits have remained elusive. Here, we consider a series of popular order parameters and analyze molecular dynamics simulations of water, in the bulk and in the hydration shell of a hydrophobic solute, at 298 and 260 K. We show that these parameters are weakly correlated and probe different distortions, for example the angular versus radial disorders. We first combine these complementary descriptions to analyze the structural rearrangements leading to the density maximum in liquid water. Our results reveal no sign of a heterogeneous mixture and show that the density maximum arises from the depletion in interstitial water molecules upon cooling. In the hydration shell of the hydrophobic moiety of propanol, the order parameters suggest that the water local structure is similar to that in the bulk, with only a very weak depletion in ordered configurations, thus confirming the absence of any iceberg-type structure. Finally, we show that the main structural fluctuations that affect water reorientation dynamics in the bulk are angular distortions, which we explain by the jump hydrogen-bond exchange mechanism.