钠基蒙脱土对水分子吸附机理的第一性原理计算

First-principles Calculation of the Adsorption Mechanism of Na-montmorillonite for Water Molecules

钠基蒙脱土吸水膨胀是造成深部巷道中软岩膨胀的主要原因。为了解决钠基蒙脱土吸水膨胀带来的工程安全问题,本文基于量子力学的第一性原理,利用材料模拟软件VASP计算模拟钠基蒙脱土对水分子吸附的机理,并研究吸附能、弹性常数与吸附量之间的关系。计算结果表明:钠基蒙脱土层间吸附水分子之后,体积主要是沿着c轴方向膨胀,体系吸附能与吸水量总体成线性正相关的关系。随着钠基蒙脱土层间水分子吸附量的增多,弹性常数C_(11)、C_(22)、C_(33)大于其他弹性常数,且C_(33)明显大于C_(11)、C_(22)。此外,钠基蒙脱土的体积模量B、剪切模量G、杨氏模量E都随吸水量的增加而减小。该计算结果为解决钠基蒙脱土相关的工程安全问题提供了理论指导。

The main cause of soft rock swelling in deep roadways is the water absorbing swelling of Na-montmorillonite.In order to solve the engineering safety problems caused by the water absorbing swelling of Na-montmorillonite,based on the first principle of quantum mechanics,this article used VASP software to calculate and simulate the mechanism of water molecule adsorption by sodium montmorillonite,and studied the relationship between adsorption energy,elastic constant and adsorption capacity.The calculation results show that after the adsorption of water molecules between the Na-montmorillonite layers,the volume mainly expands along the c-axis direction,and the adsorption energy of the system has a linear positive correlation with the water absorption.With the increase of the adsorption amount of water molecules in the Na-montmorillonite interlayer,the elastic constants C 11,C 22 and C 33 are greater than other elastic constants,and C 33 is significantly greater than C 11 and C 22.In addition,the bulk modulus B,shear modulus G and Young′s modulus E of Na-montmorillonite decreased with the increase of water absorption.The calculation results provide theoretical guidance for solving the engineering safety problems related to Na-montmorillonite.