Abstract The excess enthalpy hE and excess volume vE of the binary systems {methanol, ethanol, 1-propanol, 2-propanol, and tert-butanol + water} over the whole composition range at 298.15 K and the temperature of maximum density, TMD, in the alcohol diluted region were studied by MD simulations at atmospheric pressure. Our model systems were defined using the flexible version of the TIP4P/2005 model of water, the OPLS-AA for alcohols, and the geometric combining rule for all the Lennard-Jones cross interactions, with the exception of those between oxygen sites of water and alcohol molecules. These latter values were fitted to reproduce the experimental excess properties of the mixtures. This new parameterization allows for an appropriate description of the excess thermodynamics of these short-chain alcohol/water systems over the whole composition range. The changes in the temperature of maximum density of water induced by the addition of small amounts of alcohol concentration are, however, not adequately reproduced by our models. In all instances we observe a pronounced decrease of the simulated TMDs when alcohol concentration increases. This is in sharp contrast with the experimental behavior, which at very high dilution displays slight increases in the TMD right before the decreasing regime sets in for higher alcohol concentrations. For similar alcohol mole fractions, the simulated decrease of the TMDs grows in parallel with the size of the alkyl group of the alcohol. A similar situation is found experimentally for concentrations higher than those that increase the TMD. These differences disappear when the TMD change is expressed in terms of the mass concentration of alcohol. This leads to very similar Despretz constants for all solutions studied in this work.

中文翻译：

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短链醇水溶液的分子动力学模拟。过大的特性和最大密度的温度

摘要 二元体系 {甲醇、乙醇、1-丙醇、2-丙醇和叔丁醇 + 水} 在整个组成范围内在 298.15 K 和最大密度温度 TMD 下的过量焓 hE 和过量体积 vE，在大气压下通过 MD 模拟研究了酒精稀释区域中的 。我们的模型系统是使用 TIP4P/2005 水模型的灵活版本、醇类的 OPLS-AA 以及所有 Lennard-Jones 交叉相互作用的几何组合规则定义的，但水和氧的氧位点之间的相互作用除外。酒精分子。这些后面的值被拟合以再现混合物的实验过度特性。这种新的参数化允许对这些短链醇/水系统在整个组成范围内的过量热力学进行适当的描述。然而，我们的模型不能充分再现由添加少量酒精浓度引起的最大水密度温度的变化。在所有情况下，当酒精浓度增加时，我们观察到模拟 TMD 显着降低。这与实验行为形成鲜明对比，实验行为在非常高的稀释度下显示出 TMD 的轻微增加，就在降低方案设置为更高的酒精浓度之前。对于相似的醇摩尔分数，模拟的 TMD 减少与醇的烷基大小平行增长。对于高于那些增加 TMD 的浓度，实验发现了类似的情况。当 TMD 变化以酒精的质量浓度表示时，这些差异就会消失。这导致本工作中研究的所有解决方案的 Despretz 常数非常相似。