Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule Zurich and Facoltà di Informatica, Instituto di Scienze Computationali, Università della Svizzera Italiana, CH-6900 Lugano, Switzerland.
Proc Natl Acad Sci U S A. 2014 Mar 4;111(9):3310-5. doi: 10.1073/pnas.1400675111. Epub 2014 Feb 12.
The dynamics of water exhibits anomalous behavior in the presence of different electrolytes. Recent experiments [Kim JS, Wu Z, Morrow AR, Yethiraj A, Yethiraj A (2012) J Phys Chem B 116(39):12007-12013] have found that the self-diffusion of water (Dw) can either be enhanced or suppressed around CsI and NaCl, respectively, relative to that of neat water. Here we show that unlike classical empirical potentials, ab initio molecular dynamics simulations successfully reproduce the qualitative trends observed experimentally. These types of phenomena have often been rationalized in terms of the "structure-making" or "structure-breaking" effects of different ions on the solvent, although the microscopic origins of these features have remained elusive. Rather than disrupting the network in a significant manner, the electrolytes studied here cause rather subtle changes in both structural and dynamical properties of water. In particular, we show that water in the ab initio molecular dynamics simulations is characterized by dynamic heterogeneity, which turns out to be critical in reproducing the experimental trends.
在存在不同电解质的情况下，水的动力学表现出异常行为。最近的实验[Kim JS、Wu Z、Morrow AR、Yethiraj A、Yethiraj A（2012）J Phys Chem B 116（39）：12007-12013]发现，相对于纯水，CsI 和 NaCl 周围的水（Dw）自扩散可以增强或抑制。在这里，我们表明，与经典经验势不同，从头分子动力学模拟成功地再现了实验中观察到的定性趋势。这些类型的现象通常可以根据不同离子对溶剂的“结构形成”或“结构破坏”效应来解释，尽管这些特征的微观起源仍然难以捉摸。这里研究的电解质并没有以显著的方式破坏网络，而是对水的结构和动力学性质产生了相当微妙的变化。特别是，我们表明，从头分子动力学模拟中的水具有动态异质性，这对于再现实验趋势至关重要。
