阐明液态水和氨中π-氢键的本质
Elucidating the Nature of $π$-hydrogen Bonding in Liquid Water and Ammonia
AI总结：
本研究通过机器学习势增强的从头算路径积分分子动力学模拟，阐明了液态水和氨中苯周围π-氢键的结构、动力学及光谱特征，并揭示了水中特有的反协同效应，为经验力场描述提供了参考。
摘要：
芳香族化合物与水分子和氨分子形成一种不寻常的氢键，称为π-氢键。在这项工作中，我们报告了由机器学习势增强的从头算路径积分分子动力学模拟，以研究苯在液态水和氨中溶液的结构、动力学和光谱性质。具体而言，我们对苯分子周围溶剂的空间分布函数进行建模，确立π-氢键相互作用作为一个突出的结构基序，并建立存在判据以区分π-氢键构型。这些作为计算溶剂分子在π-氢键中结合亲和力的结构基础，识别出水中芳香环上的反协同效应（但在氨中不存在），并估计了两种溶剂中π-氢键的寿命。最后，我们模拟了水化壳层分辨的振动光谱，以清晰识别我们模拟中这一结构基序的振动特征。这些分解的光谱证实了先前苯在水中的实验发现，提供了额外的见解，并进一步强调了水和氨中π-氢键之间的对比。我们的模拟为所研究的现象提供了全面的图像，同时作为使用经验力场在更复杂情况（如生物界面水化）中准确描述π-氢键的有意义的从头算参考。
英文摘要：
Aromatic compounds form an unusual kind of hydrogen bond with water and ammonia molecules, known as the $π$-hydrogen bond. In this work, we report ab initio path integral molecular dynamics simulations enhanced by machine-learning potentials to study the structural, dynamical, and spectroscopic properties of solutions of benzene in liquid water and ammonia. Specifically, we model the spatial distribution functions of the solvents around the benzene molecule, establish the $π$-hydrogen bonding interaction as a prominent structural motive, and set up existence criteria to distinguish the $π$-hydrogen bonded configurations. These serve as a structural basis to calculate binding affinities of the solvent molecules in $π$hydrogen bonds, identify an anticooperativity effect across the aromatic ring in water (but not ammonia), and estimate $π$-hydrogen bond lifetimes in both solvents. Finally, we model hydration-shell-resolved vibrational spectra to clearly identify the vibrational signature of this structural motif in our simulations. These decomposed spectra corroborate previous experimental findings for benzene in water, offer additional insights, and further emphasize the contrast between $π$-hydrogen bonds in water and in ammonia. Our simulations provide a comprehensive picture of the studied phenomenon and, at the same time, serve as a meaningful \textit{ab initio} reference for an accurate description of $π$-hydrogen bonding using empirical force fields in more complex situations, such as the hydration of biological interfaces.
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