水对无定形SiO_2拉伸特性影响的反应分子动力学模拟  

Influence of water on the tensile properties of amorphous silica: a reactive molecular dynamics simulation

作　　者：张云安[1] 陶俊勇[1] 陈循[1] 刘彬[1] 

机构地区：[1]国防科学技术大学机电工程与自动化学院国防科学技术大学装备综合保障技术重点实验室,长沙410073

出　　处：《物理学报》2013年第24期258-264,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51175503)资助的课题~~

摘　　要：潮湿对SiO2的强度有重要影响.采用反应场分子动力学模拟方法,研究液态水对无定形SiO2(a-SiO2)准静态拉伸特性的影响.准静态拉伸模拟的结果表明,在干燥条件下,a-SiO2的拉伸强度为9.4 GPa,而在含液态水时则下降为4.7 GPa,表明液态水使得a-SiO2拉伸强度发生显著下降.根据应力-应变曲线分析可知,干燥条件下a-SiO2结构的刚度随着拉伸应变的增加保持稳定,而含液态水的a-SiO2刚度随着拉伸应变的增加而逐步降低,并且应变为16%—20%时的应力-应变曲线类似于金属的屈服现象.通过对拉伸过程的原子图像分析可知,含液态水a-SiO2的拉伸过程并没有发生塑性变形,而是因为应力增大加速了水解反应,使得应力-应变曲线表现出上述塑性现象.Humidity has an important influence on the strength of the silica（SiO2）. We examine the influence of liquid water on the tensile properties of amorphous silica（a-SiO2） using reactive molecular dynamics simulation. The results of the quasi-static tension show that liquid water reduces the tensile strength of a-SiO2 significantly. The tensile strength of dry a-SiO2 is 9.4 GPa while the tensile strength of a-SiO2 in the presence of liquid water is only 4.7 GPa. The strain-stress curve of dry a-SiO2 indicates that the stiffness of the a-SiO2 structure becomes stable with the increase of strain. On the other hand, the stiffness of the a-SiO2 with liquid water is gradually reduced with the increase of tensile strain. Moreover, the strain-stress curve of a-SiO2 in a strain range of 16% to 20% in the presence of liquid water is similar to the yielding phenomenon of plastic metal. The snapshots of the a-SiO2 in the presence of liquid water during the tension show that no plastic deformation is observed. We propose that the stress-enhanced hydrolysis releases part of the stress for the rupture of the Si—O bonds, so that the stiffness of the a-SiO2 in the presence of liquid water decreases with the increase of strain.

关 键 词：无定形SiO_2 机械强度 水 分子动力学模拟 

分 类 号：O613.72[理学—无机化学]