Quantum nature of the hydrogen bond
Quantum nature of the hydrogen bond
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DOI：
10.1073/pnas.1016653108
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发表时间：
2011-04-19
影响因子：
11.1
通讯作者：
Michaelides, Angelos
中科院分区：
文献类型：
--
作者：
Li, Xin-Zheng;Walker, Brent;Michaelides, Angelos
氢键是弱的，通常是分子间的键，它将许多软物质以及水、网络液体和许多铁电晶体的凝聚相保持在一起。氢的小质量意味着它们本质上是量子力学的，必须考虑零点运动和隧穿等效应，尽管这些效应通常不被考虑。作为一个突出的例子，量子核效应对氢键强度的影响以及氢键系统的结构仍然缺乏清晰的图像。在这里，我们报告从头算路径积分分子动力学研究的量子性质的氢键。通过对大量氢键系统的系统研究，我们发现量子核效应削弱了弱氢键，但加强了相对较强的氢键。这种简单的相关性来自于非谐分子间键弯曲和分子内键拉伸之间的竞争。提供了一个简单的经验法则，使预测氢键键合的材料一般仅与经典知识（如氢键强度或氢键长度）。我们的工作合理化了量子核效应的影响，这可能导致氢键的削弱或加强，以及相应的结构，在广泛的氢键材料。此外，它强调了需要允许灵活的分子时，非谐势用于基于力场的量子核效应的研究。
Hydrogen bonds are weak, generally intermolecular bonds, which hold much of soft matter together as well as the condensed phases of water, network liquids, and many ferroelectric crystals. The small mass of hydrogen means that they are inherently quantum mechanical in nature, and effects such as zero-point motion and tunneling must be considered, though all too often these effects are not considered. As a prominent example, a clear picture for the impact of quantum nuclear effects on the strength of hydrogen bonds and consequently the structure of hydrogen bonded systems is still absent. Here, we report ab initio path integral molecular dynamics studies on the quantum nature of the hydrogen bond. Through a systematic examination of a wide range of hydrogen bonded systems we show that quantum nuclear effects weaken weak hydrogen bonds but strengthen relatively strong ones. This simple correlation arises from a competition between anharmonic intermolecular bond bending and intramolecular bond stretching. A simple rule of thumb is provided that enables predictions to be made for hydrogen bonded materials in general with merely classical knowledge (such as hydrogen bond strength or hydrogen bond length). Our work rationalizes the influence of quantum nuclear effects, which can result in either weakening or strengthening of the hydrogen bonds, and the corresponding structures, across a broad range of hydrogen bonded materials. Furthermore, it highlights the need to allow flexible molecules when anharmonic potentials are used in force field-based studies of quantum nuclear effects.