非静水压作用下石膏电学性质的理论研究

Theoretical study on the electrical properties of gypsum under non-hydrostatic pressure

地球内部广泛存在着差应力,这些外在因素的存在影响着矿物的性质,而矿物的电学性质与结构相变息息相关.为了更加了解地球内部结构与动力学过程,采用第一性原理方法,在等效平衡压0~10 GPa范围内计算地球内部浅层矿物石膏在静水压和非静水压条件下的电学性质.计算结果表明:静水压和非静水压条件下无水石膏的密度和带隙变化基本一致,但二水石膏的密度和带隙在非静水压为6 GPa附近发生突变,这可能是由于非静水压环境使晶体结构更容易发生畸变,更有利于水分子氢键网络的重新排列和CaSO_(4)层间结构的塌缩,因此非静水压下可能更加有利于二水石膏在高温高压下的脱水反应.这对理解地幔中矿物的脱水和储水产生重大的影响,为理解地幔中矿物的脱氢和储水提供理论依据.

There is a wide range of differential stresses in the Earth’s interior.These external factors affect the properties of minerals,and the electrical properties of minerals are closely related to structural phase transitions.In order to better understand the internal structure and dynamic process of the Earth,the electrical properties of the shallow mineral gypsum in the Earth’s interior under hydrostatic and non-hydrostatic pressure were calculated by using the first-principles method in the range of equivalent equilibrium pressure 0~10 GPa.The results show that:the densities and band gaps of anhydrite under hydrostatic and non-hydrostatic conditions are basically the same,but the densities and band gaps of gypsum change rapidly near the non-hydrostatic pressure of 6 GPa,which may be because the non-hydrostatic environment makes the crystal structure more prone to distortion,which is more conducive to the rearrangement of hydrogen bond network of water molecules and the collapse of interlayer structure of CaSO_(4).Therefore,non-hydrostatic pressure may be more conducive to the dehydration reaction of gypsum at high temperature and high pressure.This has a great impact on the understanding of the dehydration and water storage of minerals in the mantle,and provides a theoretical basis for the understanding of the dehydrogenation and water storage of minerals in the mantle.