Molecular dynamics computer simulations have been conducted for ethanol–water liquid mixtures in the water-rich side of the composition range, with 10, 20, and 30 mol % of alcohol, at temperatures between room temperature and the experimental freezing point of the given mixture. All-atom-type (optimized potential for liquid simulations) interatomic potentials have been assumed for ethanol, in combination with two kinds of rigid water models (SPC/E and TIP4P/2005). Both combinations have provided excellent reproductions of the experimental X-ray total structure factors at each temperature; this yielded a strong basis for further structural analyses. Beyond partial radial distribution functions, various descriptors of hydrogen-bonded assemblies, as well as of the hydrogen-bonded network have been determined. A clear tendency was observed toward that an increasing proportion of water molecules participate in hydrogen bonding with exactly two donor and two acceptor sites as temperature decreases. Concerning larger assemblies held together by hydrogen bonding, the main focus was put on the properties of cyclic entities: it was found that, similarly to methanol–water mixtures, the number of hydrogen-bonded rings has increased with lowering temperature. However, for ethanol–water mixtures, the dominance of 5-fold rings, and not 6-fold rings, could be observed.

中文翻译：

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冷却过程中乙醇-水混合物中氢键和氢键网络的变化

在室温至给定混合物的实验凝固点之间的温度下，对组成范围内富水一侧的乙醇-水液体混合物进行了分子动力学计算机模拟，其中乙醇含量为10、20和30 mol％ 。结合两种刚性水模型（SPC / E和TIP4P / 2005），已假定乙醇的全原子类型（液体模拟的最佳电势）原子间电势。两种组合均提供了每个温度下实验X射线总结构因子的出色再现；这为进一步的结构分析奠定了坚实的基础。除了部分径向分布函数以外，还确定了氢键组装体以及氢键网络的各种描述符。观察到明显的趋势，随着温度降低，越来越多的水分子参与与两个供体和两个受体位点的氢键键合。关于通过氢键固定在一起的较大组装体，主要重点放在环状实体的性质上：发现与甲醇-水混合物相似，氢键合环的数目随着温度的降低而增加。但是，对于乙醇-水混合物，可以观察到5环而不是6环的优势。与甲醇-水混合物相似，氢键环的数量随着温度的降低而增加。但是，对于乙醇-水混合物，可以观察到5环而不是6环的优势。与甲醇-水混合物相似，氢键环的数量随着温度的降低而增加。但是，对于乙醇-水混合物，可以观察到5环而不是6环的优势。