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arXiv 1504.02537cond-mat.mtrl-scinucl-th
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石英中辐射致缺陷的性质

Nature of Radiation-Induced Defects in Quartz

Bu Wang, Yingtian Yu, Isabella Pignatelli, Gaurav N. Sant, Mathieu Bauchy

摘要:

虽然石英($\rm α$ -形式)是在辐射暴露是一个问题的许多应用中使用的矿物,但在辐射诱导损伤期间形成的原子缺陷的性质尚未完全澄清。特别是,氧空位形成的程度仍然是有争议的,这是一个首要的问题,因为光学技术的基础上,带电的氧空位已被用来评估石英的辐射损伤水平。本文采用分子动力学(MD)模拟方法研究了弹道撞击对石英原子网络的影响。我们发现,形成的缺陷主要由过配位的Si和O以及Si-O连接缺陷组成,例如,小的Si-O环和共边Si四面体。氧空位,相反,被发现在相对较低的丰度,这表明表征的基础上$E^{\prime}$中心不足以捕捉辐射引起的结构损伤石英。最后,我们评估依赖于入射能量,形成的每种类型的点缺陷的量,并明确量化的阈值位移能为O和Si原子。这些结果提供了一个全面的基础,以评估石英辐射损伤的性质和程度。

英文摘要:

Although quartz ($\rm α$-form) is a mineral used in numerous applications wherein radiation exposure is an issue, the nature of the atomistic defects formed during radiation-induced damage have not been fully clarified. Especially, the extent of oxygen vacancy formation is still debated, which is an issue of primary importance as optical techniques based on charged oxygen vacancies have been utilized to assess the level of radiation damage in quartz. In this paper, molecular dynamics (MD) simulations are applied to study the effects of ballistic impacts on the atomic network of quartz. We show that the defects that are formed mainly consist of over-coordinated Si and O, as well as Si--O connectivity defects, e.g., small Si--O rings and edge-sharing Si tetrahedra. Oxygen vacancies, on the contrary, are found in relatively low abundance, suggesting that characterizations based on $E^{\prime}$ centers do not adequately capture radiation-induced structural damage in quartz. Finally, we evaluate the dependence on the incident energy, of the amount of each type of the point defects formed, and quantify unambiguously the threshold displacement energies for both O and Si atoms. These results provide a comprehensive basis to assess the nature and extent of radiation damage in quartz.

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