【摘要】 缓冲回填材料是高放废物地质处置库中的关键工程屏障，以膨润土作为主要基材，起着阻隔核素迁移和维护处置库长期安全稳定等作用。膨润土中蒙脱石矿物含量较高，结合水的存在对其水化膨胀、收缩、孔隙结构、土水特性、强度及变形等物理力学性质，以及电导率、阳离子交换容量、吸附热等电化学性质产生重要影响。对膨润土中蒙脱石矿物吸附水性能进行分子层面模拟，基于颗粒表面物理-化学相关理论，运用Monte Carlo、Molecular Mechanics UFF等系列方法，综合确定蒙脱石结合水后分子层间距和密度，讨论交换性阳离子类型及含量对结合水膜厚度和密度的影响。结果表明：蒙脱石分子层间距与水含量正相关，密度与水含量负相关；模型优化前后构型发生较大变化，在构型优化前范德华力对总能量的贡献最多，而优化后以非价键作用的静电作用和价键作用的角弯曲为主。更多还原

【Abstract】 The buffer material is the key engineering barrier for high-level radioactive waste repository, with bentonite as the main substrate, which prevents the migration of nuclides and keeps the canister in its centered position in the deposition hole as long as required with respect to the safety of the repository. The high montmorillonite mineral content in bentonite combined with the presence of water has important effects on the physical and mechanical properties such as hydration expansion, shrinkage, pore structure, soil-water characteristics, strength, deformation, as well as electrochemical properties such as conductivity, cation exchange capacity, and adsorption heat, etc. These physical and chemical properties are particularly critical for the buffer backfill material to block the migration of radionuclides. In this paper, molecular-level simulations of water adsorption in montmorillonite were carried out based on the physical and chemical theories related to particle surface, using a series of methods including Monte Carlo Method, Molecular Mechanics UFF, etc. The molecular spacing and density of montmorillonite after water absorption were comprehensively determined. The effects of exchangeable cation types and contents on the thickness and density of the adsorbed water film were discussed. The results show that the molecular spacing of montmorillonite is positively correlated with the water content, while the density is negatively correlated with the water content. The configuration undergoes significant changes before and after the model optimization,with van der Waals force contributing the most to the total energy before optimization and electrostatic interaction of non-bonded and angle bending of bond interaction becoming the main factors after optimization.更多还原