方石英的亚稳态形成机制探讨  

DISCUSSION ON METASTABLE FORMATION MECHANISM OF CRISTOBALITE1

作　　者：肖万生[1] 陈晋阳[1] 彭文世[1] 翁克难[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640

出　　处：《矿物岩石》2003年第4期5-10,共6页Mineralogy and Petrology

基　　金：中国科学院知识创新工程重要方向项目(No.KJCX2-SW-N03)

摘　　要：　方石英形成于石英或鳞石英热力学稳定区是一种普遍的现象,并基本上是由非晶态SiO2转变而成。方石英的这种亚稳态形成机制可用Ostwald分步规则这一动力学经验规律来阐述;而引起非晶态SiO2转变成方石英的速率常数大大高于方石英转变成石英或鳞石英的速率常数的本质是非晶态SiO2局部中程有序结构与β-方石英的动态无序结构的相似性;这种相似性使非晶态SiO2结晶过程中β-方石英的有效成核速率大大增加,并最终导致亚稳态方石英的形成。非晶态SiO2中所含的杂质元素有利于降低方石英的形成温度,加速反应进程,但对于亚稳态方石英的形成没有决定作用,除非这些杂质元素有利于方石英结构的稳定性。The cristobalite,transformed from amorphous silica basically,is ubiquitous in the thermodynamic stable region of quartz or tridymite.This formation mechanism of cristobalite metastability may be explained by the Ostwald′s stage rule which is an experiential dynamic principle.The key factor which results in that the rate constant is higher in the process of the amorphous silica to transform to cristobalite than that in cristobalite to quartz or tridymite greatly is the similarity between the local intermediate range order structure for amorphous silica and the dynamic disorder structure of β-cristobalite.This statistical similarity leads to the increase of β-cristobalite valid nucleation rate greatly during the amorphous silica crystallization,and results in the formation of the metastabe cristobalite ultimately.The impure components in amorphous silica are propitious to decreasing the formation temperature of cristobalite and accelerating the reaction of amorphous silica to cristobalite.However,they are useless to formation of metastable cristobalite unless these impure components are in favor of stability of cristobalite structure.

关 键 词：方石英 非晶态SiO2 亚稳态 动力学 形成机制 

分 类 号：O657.33[理学—分析化学]