蒙脱石水化机理的分子模拟

为深入分析泥页岩水化膨胀的微观机理,采用Materials Studio(简称MS)软件,以Na-蒙脱石为研究对象,建立了蒙脱石的单晶胞和4a×2b×1c的多晶胞模型,并进行了晶格取代,添加Na+后建立了Na-蒙脱石晶体的分子模型。模拟结果显示,当蒙脱石开始吸附水分子时,水分子主要停留在Na+周围,形成水合钠离子;当分别吸附24、64和112个水分子时,分别形成第1层、第2层和第3层饱和水分子层。对Na-蒙脱石水化膨胀的微观过程进行了分子力学和分子动力学模拟,发现Na-蒙脱石的层间距和体积随吸附水分子数目的增加而增加,其密度随吸附水分子数目的增加而降低。通过晶粉衍射模拟,利用布拉格公式,计算出了Na-蒙脱石形成第1层、第2层和第3层饱和水分子层时的层间距分别为1.424 9、1.676 4和2.052 1 nm。

Molecular Simulation on Mechanism of Montmorillonite Hydration

In order to analyze the hydration mechanism of mud shale comprehensively, the unit cell and 4ax2bxlc super cellmodels of montmorillonite by applying Materials Studio software are established and the operation of lattice substitutionis conducted, as well as the Na-montmorillonite molecule model is developed after added Na+. The simulation resultsindicate that when the Na-montmorillonite begins to adsorb water, the water molecules mainly stay around Na+ and formhydration Na+. When the numbers of 24, 64 and 112 water molecules are absorbed respectively, the first, second and thirdsaturated water layer is built respectively. The molecular mechanics and dynamical mechanics for the Na-montmorilloniteare simulated, the results show that the layer distance and volume increases with more absorbed water molecules, but thedensity decreases with more water molecules. Moreover, by using Bragg’s Law, the layer distances are 1.424,9 run, 1.676,4nm and 2.052,1 nm when the first, second and third saturated water layers are gradually built up.