高岭石是煤系泥岩的主要黏土矿物组成成分之一，它的存在对泥岩的水理作用产生重要影响。高岭石与水相互作用的分子机制是深入认识泥岩遇水膨胀、软化崩解甚至泥化等现象的基础。分子动力学模拟技术是揭示物质结构与性质间关系、了解物理化学体系中物质相互作用机制的有力工具。应用巨正则系综蒙特卡洛(GCMC)及分子动力学(MD)方法对高岭石的吸水特征进行了模拟，研究了温度及压力对水分子在高岭石颗粒表面的吸附量、吸附位、吸附热、吸附能以及高岭石体积膨胀性等的影响规律，阐明了高岭石吸水的分子机制。研究结果表明:高岭石吸附水过程中，水分子和高岭石表面原子以Hw-Ok和Ow-Hk两种形式形成氢键联接;吸附热介于1.898～2.133 kJ/mol，远低于发生化学吸附的临界值42 kJ/mol，高岭石与水分子间的相互作用为典型物理吸附;吸附能为负值，高岭石吸水后体系热力学稳定，吸附能数值、吸附量及体积膨胀率变化规律相似，均随压力增加呈对数关系递增，而随温度升高递减且减幅相对较小;吸附位为吸附过程中水分子在高岭石颗粒表面某一位置出现的频次;水分子在高岭石颗粒表面的吸附依赖于分子间的范德华能和氢键作用能，压力对吸附特征的影响比温度更大，且高温不利于水分子在高岭石颗粒表面的吸附。

Kaolinite is one of the main clay mineral components of coal measures mudstone,and its existence has an important influence on the hydraulic action of mudstone.The molecular mechanism of the interaction between kaolinite and water molecules is the basis for an in-depth understanding of the phenomena of mud-stone expansion,softening,disintegration and even mudding.Molecular dynamics simulation technology is a powerful tool to reveal the relationship between material structure and properties and to understand the mechanism of matter interaction in physical and chemical systems.The water absorption characteristics of kaolinite were simulated by grand canonical ensemble Monte Carlo (GCMC) and molecular dynamics (MD) methods.The effects of temperature and pressure on the adsorption capacity,adsorption site,adsorption heat,adsorption energy and volume expansion of kaolinite particles were studied,and the molecular mechanism of water absorption of kaolinite was clarified.The results show that in the process of water molecules adsorption by kaolinite,water molecules and surface atoms of kaolinite form hydrogen bonds in the form of Hw-Ok and Ow-Hk.The adsorption heat is between 1.898 kJ/mol and 2.133 kJ/mol,which is far below the critical value of chemisorptions 42 kJ/mol,and the interaction between kaolinite and water molecules is a typical physical adsorption.The adsorption energy is negative,the thermodynamics of kaolinite system is stable after water absorption,and the changes of adsorption energy value,adsorption capacity and volume expansion are similar,which increase logarithmically with the increase of pressure,and decrease with the increase of temperature and the decrease is relatively small.The adsorption site is the frequency of water molecules appearing at a certain position on the surface of kaolinite particles during the adsorption process.The adsorption of water molecules on the surface of kaolinite particles depends on the van der Waals energy and hydrogen bonding energy between molecules,and the effect of pressure on the adsorption characteristics is greater than that of temperature,and high temperature is not conducive to the adsorption of water molecules on the surface of kaolinite particles.

1 模型构建与模拟方法

   1.1 模型构建

   1.2 模拟计算方法

2 模拟结果与分析

   2.1 吸附量

   2.2 吸附位

   2.3 吸附热

   2.4 吸附能

   2.5 体积膨胀率

3 讨论

4 结论