Water's non-tetrahedral side.
Water's non-tetrahedral side.
复制标题
DOI：
10.1039/c3fd00080j
复制
发表时间：
2013-06
影响因子：
3.4
通讯作者：
Richard H. Henchman;Stuart J Cockram
中科院分区：
文献类型：
--
作者：
Richard H. Henchman;Stuart J Cockram
提出了液态水具有非四面体配位和四面体配位的情况。鉴于氢键定义的结构的依赖性，最近的概念突破是拓扑氢键定义，它克服了传统的基于截止的氢键定义的缺点。它确定了水的第一配位壳层中的氢键，使用假设的过渡态作为边界，而不是固定的截止值。在这里，拓扑定义被应用到液态水的氢键的距离，角度和能量的不同类型的协调发现，这些协调包括弯曲，三角，四面体，三角双锥，八面体结构，以及分叉氢，分叉氧和环状二聚体，和更大的多边形。所有物种都显示出与它们的分类相一致的特性，证明了它们的分配，并支持水作为连续的单相混合物的结构。然而，一个详细的分析，以评估假设的过渡态的存在揭示了显着的发现，氢键切换通过分叉的氢在某些情况下是一个无势垒的过程。转换的可能性取决于受体数量和供体与受体的接近程度。具体地，受体的最外层亚壳层中的供体向上切换到与起始受体具有相同或更高配位的受体，向下切换到具有两个或更多个更低配位的受体，或者如果新受体具有仅低一个的配位，则位于两个受体之间分叉。它是哪一种密切取决于供体分子的振荡和控制附近受体配位的其他氢键开关。最后，进行了搜索的长程结构在水中的施主-受主偏置的分布的不对称性，但没有发现。
The case for liquid water having non-tetrahedral as well as tetrahedral coordination is put forward. Given the dependence of structure on the hydrogen bond definition, a recent conceptual breakthrough has been the topological hydrogen bond definition which overcomes the shortcomings of traditional cut-off-based hydrogen bond definitions. It identifies the hydrogen bonds in water's first coordination shell using assumed transition states as boundaries instead of fixed cut-offs. Here, the topological definition is applied to liquid water to characterise the distances, angles and energies of the hydrogen bonds for the different types of coordinations found. These coordinations include bent, trigonal, tetrahedral, trigonal bipyramidal, and octahedral structures, as well as bifurcated hydrogens, bifurcated oxygens and cyclic dimers, and larger polygons. All species are shown to have properties consistent with their classification, justifying their assignments, and supporting the structure of water as a continuous, single phase mixture. However, a detailed analysis to assess the existence of the assumed transition states reveals the remarkable finding that hydrogen bond switching via a bifurcated hydrogen under certain circumstances is a barrierless process. The likelihood of a switch depends on both the acceptor numbers and on the proximity of a donor to its acceptor. Specifically, a donor in an acceptor's outermost subshell switches uphill to an acceptor of the same or higher coordination to the starting acceptor, downhill to an acceptor of lower coordination by two or more, or sits bifurcated between two acceptors if the new acceptor has a coordination lower by only one. Which it is depends intimately on the donor molecule's oscillations and on other hydrogen bond switches that control the nearby acceptors' coordinations. Finally, a search is conducted for long-range structure in water in terms of asymmetry in the distribution of the donor-acceptor bias but none is found.