Pressure dependence of the electronic structure in kaolinite: A first-principles study

Using the first-principle methods, the pressure dependence of the electronic structure and band structure of kaolinite were studied within the local-density approximation. The calculated results show that pressure would chiefly alter the band structure of kaolinite, while pressure can have its main effect on the band gap of kaolinite. At p = 0.6 GPa, band structure of kaolinite first converts an indirect gap into a direct gap, and then recovers an indirect gap structure at p = 66.2 GPa because CBM shift in the band structure is under high-pressure. The bond Si–O is more stable than bond Al–O under pressure, in addition, pressure has a significant effect on the inner hydroxyl bond of kaolinite and leads to a large variation of H–O(inner) bond lengths. The calculated results will not only help to understand the electronic structure of kaolinite under pressure, but also provide theoretical guidance for deal with the safe problems of soft-rock tunnel engineering.