Montmorillonite is the main mineral source for the swelling and shrinking of expansive soils. The macroscopic phenomena of soil are affected by the action of deep-level nanosized minerals. In order to illustrate the nanoscale mechanism from the molecular level, a combination of Monte Carlo and molecular dynamics was used to explore the swelling and shrinking characteristics of montmorillonite. The results showed that the basal spacing, free swelling ratio, and void ratio were positively correlated with water content but were inversely proportional to the change of CEC. The hysteresis phenomena of swelling and shrinking were the most significant at a water content of 40%. Compared with the expansive soil, the nanoscale shrinkage curve of montmorillonite also included three stages of normal shrinkage, residual shrinkage, and no shrinkage. The relative concentration of water molecules conveyed information such as the thickness and position of the hydration film and explained the difference in swelling and shrinking caused by the above variables. The changes in the number and length of hydrogen bonds revealed the order of formation and the process of destruction of hydrogen bonds during the reaction. The similarity of the trends between the basal spacing, binding energy, and the number of hydrogen bonds indicated that the swelling and shrinking of the crystal layer are a reflection of the molecular interaction, and the hydrogen bonding is particularly critical.

中文翻译：

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基于蒙特卡罗和分子动力学的纳米蒙脱石溶胀收缩行为模拟研究

蒙脱石是膨胀土膨胀和收缩的主要矿物来源。土壤的宏观现象受深层次纳米矿物的作用影响。为了从分子水平说明纳米尺度的机理，结合蒙特卡罗和分子动力学，探索蒙脱石的膨胀和收缩特性。结果表明，基间距、自由膨胀率和空隙率与含水量呈正相关，与CEC的变化成反比。膨胀和收缩的滞后现象在含水量为 40% 时最为显着。与膨胀土相比，蒙脱石的纳米级收缩曲线还包括正常收缩、残余收缩和无收缩三个阶段。水分子的相对浓度传达了水化膜的厚度和位置等信息，并解释了由上述变量引起的膨胀和收缩的差异。氢键数量和长度的变化揭示了反应过程中氢键的形成顺序和破坏过程。基间距、结合能和氢键数之间趋势的相似性表明，晶体层的膨胀和收缩是分子相互作用的反映，其中氢键尤为关键。氢键数量和长度的变化揭示了反应过程中氢键的形成顺序和破坏过程。基间距、结合能和氢键数之间趋势的相似性表明，晶体层的膨胀和收缩是分子相互作用的反映，其中氢键尤为关键。氢键数量和长度的变化揭示了反应过程中氢键的形成顺序和破坏过程。基间距、结合能和氢键数之间趋势的相似性表明，晶体层的膨胀和收缩是分子相互作用的反映，其中氢键尤为关键。