Computer simulation of defect clusters in UO2 and their dependence on composition
Computer simulation of defect clusters in UO2 and their dependence on composition
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DOI：
10.1016/j.jnucmat.2014.10.001
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发表时间：
2015-01-01
影响因子：
3.1
通讯作者：
Storr, M. T.
中科院分区：
文献类型：
--
作者：
Brincat, N. A.;Molinari, M.;Storr, M. T.
人们认识到，点缺陷在许多技术上重要的氧化物的行为和性能中起着关键作用。人们不太了解的是这些缺陷是如何聚集在一起的，以及至关重要的是，这些缺陷在多大程度上随着成分的变化而变化。我们选择通过考虑UO2来研究这一现象，UO2是一种核燃料材料，文献中关于缺陷聚类作为氧含量函数的数据相互矛盾。早期对萤石UO2+x的研究提出了一种基于2:2:2 Willis簇的模型，而最近的研究则提出了立方面体或分裂的四间隙缺陷簇。在这里，我们使用PBE + U泛函模拟有缺陷的UO2+x，发现当0.125 < x < 0.25时，边共享2:2:2的Willis簇链是最稳定的。当x = 0.125时，这些氧链不稳定，转变为分裂的双间隙团簇，这表明存在的氧团簇类型取决于当地环境和化学计量。爱思唯尔B.V.版权所有
It is recognised that point defects play a key role in the behaviour and properties of many technologically significant oxides. What is less well understood is how these defects cluster together and, crucially, the extent to which the clusters change with composition. We chose to investigate this phenomenon by considering UO2, a nuclear fuel material for which there is contradictory data in the literature concerning defect clustering as a function of oxygen content. Early studies of fluorite UO2+x proposed a model based on 2:2:2 Willis clusters whilst more recent research suggests cuboctahedral or split quad-interstitial defect clustering. Here we use the PBE + U functional to simulate defective UO2+x and find for 0.125 < x < 0.25, chains of edge-sharing 2:2:2 Willis clusters to be most stable. Below x = 0.125 these chains destabilise, transforming in to split di-interstitial clusters, demonstrating that the type of oxygen cluster present is dependent on local environment and stoichiometry. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.