高岭石脱水分子动力学及密度泛函研究

Molecular Dynamics and Density Functional Study of Kaolinite Dehydration

利用分子动力学对高岭石脱水过程进行模拟,并采用密度泛函理论分析其脱水机理.结果表明：在300～600K时高岭石并未发生明显变化,在700K之后高岭石中Al配位数逐渐降低,H配位数逐渐增高,X射线衍射图谱显示其中的氧化铝相对含量逐渐增高,高岭石发生脱水反应.脱水机理为在温度影响下Al的3p轨道中部分电子向相键连的羟基中O的2p轨道发生转移,使得Al—OH键活化,经活化后羟基中O的2p轨道与相邻羟基中H的1s轨道形成杂化轨道.

Molecular dynamics was used to simulate the dehydration process of kaolinte,and density functional theory was utilized to analyze the dehydration mechanism.The results show that significant changes of kaolinite are not found at 300-600 K,and in contradistinction to gradually increasing trend of coordination number of H atom,coordination number of Al atom is shown to decrease gradually after 700 K,and it is showed in kaolinite XRD pattern that the relative content of alumina increases gradually,which indicates that the dehydration of kaonilite takes place in the process.The analysis on the dehydration mechanism reveals that the electronic transfer mainly occurs between 3p of Al and 2p of O in hydroxyl that is connected to the Al atom,and hybrid orbital is generated between 2p of O in the activated hydroxyl and 1s of H in the adjacent hydroxyl.