Henchman Richard H
Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
J Phys Condens Matter. 2016 Sep 28;28(38):384001. doi: 10.1088/0953-8984/28/38/384001. Epub 2016 Jul 22.
A model is proposed for liquid water that is a continuum between the ordered state with predominantly tetrahedral coordination, linear hydrogen bonds and activated dynamics and a disordered state with a continuous distribution of multiple coordinations, multiple types of hydrogen bond, and diffusive dynamics, similar to that of normal liquids. Central to water's heterogeneous structure is the ability of hydrogen to donate to either one acceptor in a conventional linear hydrogen bond or to multiple acceptors as a furcated hydrogen. Linear hydrogen bonds are marked by slow, activated kinetics for hydrogen-bond switching to more crowded acceptors and sharp first peaks in the hydrogen-oxygen radial distribution function. Furcated hydrogens, equivalent to free, broken, dangling or distorted hydrogens, have barrierless, rapid kinetics and poorly defined first peaks in their hydrogen-oxygen radial distribution function. They involve the weakest donor in a local excess of donors, such that barrierless whole-molecule vibration rapidly swaps them between the linear and furcated forms. Despite the low number of furcated hydrogens and their transient existence, they are readily created in a single hydrogen-bond switch and free up the dynamics of numerous surrounding molecules, bringing about the disordered state. Hydrogens in the ordered state switch with activated dynamics to make the non-tetrahedral coordinations of the disordered state, which can also combine to make the ordered state. Consequently, the ordered and disordered states are both connected by diffusive dynamics and differentiated by activated dynamics, bringing about water's continuous heterogeneity.
本文提出了一种液态水模型，该模型介于主要具有四面体配位、线性氢键和活化动力学的有序状态与具有多种配位连续分布、多种氢键类型和扩散动力学（类似于普通液体）的无序状态之间。水的异质结构的核心在于氢能够在传统线性氢键中向一个受体供体，或者作为分叉氢向多个受体供体。线性氢键的特征是氢键切换到更拥挤受体的动力学缓慢且活化，以及氢 - 氧径向分布函数中的尖锐第一峰。分叉氢，等同于自由、断裂、悬空或扭曲的氢，具有无障碍、快速的动力学，并且在其氢 - 氧径向分布函数中第一峰定义不明确。它们涉及局部供体过量中的最弱供体，使得无障碍的全分子振动能迅速在其线性和分叉形式之间交换它们。尽管分叉氢数量少且存在短暂，但它们很容易在单个氢键切换中产生，并释放许多周围分子的动力学，从而导致无序状态。有序状态下的氢通过活化动力学进行切换，形成无序状态的非四面体配位，无序状态也可以组合形成有序状态。因此，有序状态和无序状态通过扩散动力学相互连接，并通过活化动力学相互区分，从而导致水的连续异质性。
