水合过量质子的跳跃机制及其对水中质子扩散的贡献
The Hopping Mechanism of the Hydrated Excess Proton and Its Contribution to Proton Diffusion in Water
AI总结：
本文通过分析水合过量质子的 AIMD 轨迹并过滤往复回跳事件，澄清质子跳跃主要源于 rattling，而非多数为协同多重跳跃，且结果与 special-pair dance 模型及实验时间尺度相符。
摘要：
在本工作中，对水中水合过量质子的从头算分子动力学（AIMD）模拟进行了一系列分析，以量化协同跳跃事件和“rattling（往复振荡）”事件的相对发生情况，从而进一步阐明水中质子输运的跳跃机制。与某些早期论文报道的结果相反，新的分析发现，协同跳跃事件确实在所有模拟中都会发生，但大多数事件是质子往复振荡的产物，即过量质子会在两个或更多水分子之间往复振荡。这些结果与所提出的水合过量质子“special-pair dance（特殊对之舞）”模型一致；在该模型中，质子转移的受体水分子会快速变化（在三个等价的特殊对之间共振），直到发生一次决定性的质子跳跃。为了消除简单往复振荡造成的误导性影响，对轨迹应用了一个过滤器，使得随后向原水分子回跳的跳跃事件不被计入。应用该过滤器后，发现多重跳跃事件的数量急剧减少，这表明未过滤轨迹中发生的许多多重跳跃事件在很大程度上是往复振荡的产物，而非此前所认为的那样。通过比较过滤后与未过滤轨迹的连续相关函数，我们发现它们分别与质子跳跃时间和 Eigen–Zundel 相互转化时间的实验值相符。
英文摘要：
In this work a series of analyses are performed on ab initio molecular dynamics (AIMD) simulations of a hydrated excess proton in water to quantify the relative occurrence of concerted hopping events and <span>rattling</span> events, and thus to further elucidate the hopping mechanism of proton transport in water. Contrary to results reported in certain earlier papers, the new analysis finds that concerted hopping events do occur in all simulations, but that the majority of events are the product of proton rattling, where the excess proton will rattle between two or more waters. The results are consistent with the proposed <span>special-pair dance</span> model of the hydrated excess proton, wherein the acceptor water molecule for the proton transfer will quickly change (resonate between three equivalent special pairs) until a decisive proton hop occurs. To remove the misleading effect of simple rattling, a filter was applied to the trajectory such that hopping events that were followed by back hops to the original water are not counted. A steep reduction in the number of multiple hopping events is found when the filter is applied, suggesting that many multiple hopping events that occur in the unfiltered trajectory are largely the product of rattling, contrary to prior suggestions. Comparing the continuous correlation function of the filtered and unfiltered trajectories, we find agreement with experimental values for the proton hopping time and Eigen-Zundel interconversion time, respectively.
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