Density functional theory calculations of defective UO2 at U3O7 stoichiometry
Density functional theory calculations of defective UO2 at U3O7 stoichiometry
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DOI：
10.1016/j.jnucmat.2015.10.006
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发表时间：
2015-12
影响因子：
3.1
通讯作者：
Nicholas A. Brincat;M. Molinari;G. C. Allen;M. Storr;S. C. Parker
中科院分区：
文献类型：
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作者：
Nicholas A. Brincat;M. Molinari;G. C. Allen;M. Storr;S. C. Parker
二氧化铀特别容易氧化。氧化过程和由此形成的相被广泛研究。在氧化相中形成缺陷团簇，尽管它们的结构和性质尚不清楚。因此，我们研究萤石为基础的U3O7相，以确定在36原子晶胞中存在的缺陷类型。我们预测，在这个化学计量，有缺陷的结构形成氧簇和分裂四间隙簇是最稳定的缺陷。与二氧化铀相比，这些与体积收缩有关，与实验测量结果一致。氧的掺入总是与铀原子氧化成U5+有关，尽管一次计算也会导致U6+离子。由于该系统是相对不稳定的，它建议，U 4+和U 5+是在U3O7化学计量的优选氧化态。
UO2is particularly susceptible to oxidation. The oxidation processes and the phases formed as a result are widely studied. In the oxidised phases defect clusters form, although their structure and properties are unclear. Thus, we examine fluorite based U3O7phases to identify the types of defect present in a 36 atom unit cell. We predict that at this stoichiometry, defective structures form oxygen clusters and that split quad-interstitial clusters are the most thermodynamically stable defects. These are associated with a volume contraction compared to UO2, in line with experimental measurements. Incorporation of oxygen is always associated with oxidation of uranium atoms to U5+, although a single calculation leads to a U6+ion as well. As this system is relatively unstable, it is proposed that U4+and U5+are the preferred oxidation states at U3O7stoichiometry.