水动力学：氢键分叉、分子跳跃、局部密度和疏水性之间的关系
Water dynamics: Relation between hydrogen bond bifurcations, molecular jumps, local density & hydrophobicity
摘要：
水的结构和动态仍然是一个挑战。解决氢键的性质是这个难题的核心。在这里，我们采用从头算分子动力学（AIMD）模拟在很宽的温度范围内。总模拟时间约为2 ns。模拟了本体水和存在小疏水分子的水。我们表明，大角度跳跃和键分叉是水动力学的基本性质，并且它们与局部密度和氢键伸展振荡密切相关，范围从大约60到几百飞秒：局部密度差异是键分叉的驱动力和随之而来的大角度跳跃。这些跳跃与最近预测的能量不对称性密切相关。我们的分析似乎也证实了氧原子上的孤对电子提供的所谓负性轨道的存在，以使水旋转。
英文摘要：
Structure and dynamics of water remain a challenge. Resolving the properties of hydrogen bonding lies at the heart of this puzzle. Here we employ ab initio Molecular Dynamics (AIMD) simulations over a wide temperature range. The total simulation time was approx 2 ns. Both bulk water and water in the presence of a small hydrophobic molecule were simulated. We show that large-angle jumps and bond bifurcations are fundamental properties of water dynamics and that they are intimately coupled to both local density and hydrogen bond stretch oscillations in scales from about 60 to a few hundred femtoseconds: Local density differences are the driving force for bond bifurcations and the consequent large-angle jumps. The jumps are intimately connected to the recently predicted energy asymmetry. Our analysis also appears to confirm the existence of the so-called negativity track provided by the lone pairs of electrons on the oxygen atom to enable water rotation.
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