钠基蒙脱土吸附二氧化硫的第一性原理计算

First-principle calculation of SO_(2) adsorption on Na-montmorillonite

为了探索黏土矿物对污染气体的吸附作用,以钠基蒙脱土吸附二氧化硫气体分子为例,基于量子力学的第一性原理方法,利用VASP软件模拟计算钠基蒙脱土对SO_(2)气体分子的吸附机理,得出了吸附能、弹性常数与SO_(2)吸附量的关系。结果表明:在表面吸附过程中,钠基蒙脱土的top位和bridge位是SO_(2)气体分子的稳定吸附点位,SO_(2)分子被吸附后其S—O键长从1.78?减小到1.44?,O—S—O键角从119.50°减少到115.31°,而蒙脱土模型的原子键长没有明显变化;在层间吸附过程中,随着SO_(2)分子吸附量的增加,吸附能逐渐减少,蒙脱土模型的体积和c轴方向与SO_(2)吸附量成线性。弹性常数的计算结果表明,随着SO_(2)分子吸附量的增加,蒙脱土弹性常数C_(33)的变化幅度最大,降低了142.27 GPa。钠基蒙脱土结构的体积模量、剪切模量和杨氏模量都随着SO_(2)分子吸附量的增加而减少。

This paper takes Na-montmorillonite adsorption of SO_(2) molecules as an example to explore the adsorption effect of clay minerals on pollutant gases.Based on the first-principle methods of quantum mechanics,VASP is used to simulate and calculate the adsorption mechanism of Na-montmorillonite on SO_(2) molecules,finding relationship among adsorption energy,elastic constant and SO_(2) adsorption amount.The S—O bond length of adsorbed SO_(2) decreases from 1.78 to 1.44Åafter adsorption,O—S—O bond angle of adsorbed SO_(2) from 119.50°to 115.31°while bond length does not obviously change in Na-montmorillonite.In the process of interlayer adsorption,the adsorption energy gradually decreases with the increase of SO_(2) molecules adsorption.Volume and c-axis direction of the montmorillonite model are linear with the amount of SO_(2) adsorption.By calculating the montmorillonite elasticity constants under different adsorption capacity,the elasticity constant C33 perpendicular to the crystal face change grootby,decreasing by 142.27 GPa.In addition,Young's modulus,bulk modulus and shear modulus significantly decrease with the increase of SO_(2) molecules adsorption.The calculated results will provide theoretical guidance for dealing with gas pollution.