中文摘要：

蒙脱右是一种粘土矿物，为了解决软岩隧道工程中经常遇到的软岩中的蒙脱右吸水导致软岩隧道大变形的工程安全问题，需从微观的角度研究蒙脱石的物理和化学性质．使用基于密度泛雨理论（DFT）的局域密度近似（LDA）方法来研究蒙脱右的原子和电子结构．计算结果表明：Al-0的键长比Si-O的键长长，蒙脱白的价带顶（VBM）和导带底（CBM）都位于厂点，禁带宽度为5．35eV．研究表明：蒙脱石中阳离子和氧阴离子之间的化学键主要是离子键，同时也有少量的共价键，蒙脱右的价带顶（VBM）和导带底（CBM）分别由氧2p态和金属阳离子态组成．该计算结果有利于了解蒙脱石的化学和物理性质，对解决软岩隧道大变形的问题提供理论指导．

英文摘要：

Montmorillonite is a kind of clay mineral which often causes large deformation in soft -rock tunnelengineering and thus brings about safety problems in practice. To deal with these engineering safety problems, thephysical and chemical properties of montmorillonite should be studied from micro perspective. We study the atomicand electronic structures of montmorillonite by using density -functional theory within the local -densityapproximation （LDA）. The results of calculation show that Al-O bond lengths are longer than Si-O bond lengths. Itis found that both the valence band maximum （VBM） and the conduction band minimum （CBM） of montmorilloniteare at point r , and the calculated direct band gap of montmorillonite is 5.35 eV. The study shows that the chemicalbonding between cations and oxygen anions in montmorillonite is mainly ionic, as well as a minor covalentcomponent. It is pointed out that the VBM and CBM of montmorillonite consist of oxygen 2p and cations states,respectively. Our calculated results help to understand the chemical and physical properties of montmorillonite, andgive reference to the problem of large deformation of soft-rock tunnels.