Na/Al比对Na_2O-Al_2O_3-SiO_2玻璃体系微观结构的分子动力学模拟研究

Molecular dynamics simulation for effects of Na/Al ratio on microstructure in system of Na_2O-Al_2O_3-SiO_2

使用DL_POLY_2在分子动力学的基础上,采用BMH势函数,从偏径向分布函数、键角、配位数以及桥氧四个方面,模拟研究了不同Na/Al比的Na_2O-Al_2O_3-SiO_2玻璃体系微观结构。研究表明:随着Na/Al比的增加,Si—O、Al—O、O—O的键长没有变化,分别为0.160 5 nm、0.176 5 nm和0.262 5 nm,Na—O键长则逐渐减小;体系中[AlO_4]四面体的稳定性比[SiO_4]四面体差;Na/Al=2时,出现少量SiⅤ;当Na/Al比较低时,体系中出现[AlO_4]四面体的三配位现象,且未发现AlⅥ;随着Na/Al的增加,Al—T的平均配位数减少,三配位氧的含量减少。

The microstructure of the glass in the Na2O-Al2O3-SiO2 system was studied using molecular dynamic simulations employing the potential function of Born-Mayer-Huggins（ BMH）. Pair distributions functions（ PDFs） of the cations to oxygen,bond between three cations（ BAD）,coordination of the network forming cations（ CN） and the number of the bridging oxygen（ Qn） were calculated. The results indicated that the ratio of Na/Al had few influence on the bond lengths of Si—O、Al—O、O—O,which were0. 160 5 nm,0. 176 5 nm and 0. 262 5 nm,respectively. However,the bond lengths of Na—O decreased with the radio of Na/Al.The Si—O tetrahedra had the more stable structure than Al—O tetrahedra. When the ratio of Na/Al was low,AlⅥwas absent and AlⅣtricluster is present,while SiⅤwas detected in the system when Na/Al reached 2. With the increase of Na/Al,the average distribution of Al—T and the content of tricluster oxygen decreased.