科研之友
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摘要
Montmorillonite is a kind of clay mineral which often causes large deformation in soft-rock tunnel engineering and thus brings about safety problems in practice. To deal with these engineering safety problems, the physical and chemical properties of montmorillonite should be studied from basic view points. We study the atomic and electronic structures of montmorillonite by using density-functional theory with in the local-density approximation (LDA). The results of calculation show that Al-O bond lengths are longer than Si-O bond lengths. It is found that both the valence band maximum (VBM) and the conduction band minimum (CBM) of montmorillonite are at point Gamma, and the calculated direct bandgap of montmorillonite is 5.35 eV. We show that the chemical bonding between cations and oxygen anions in montmorillonite is mainly ionic, accompanied as well by a minor covalent component. 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, and are expected to be a guide for solving the problem of large deformation of soft-rock tunnels.
- 出版日期2009-7
- 单位北京应用物理与计算数学研究所; 中国矿业大学（北京）
