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arXiv 0907.1320cond-mat.mtrl-scicond-mat.str-el
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还原氧化铈中氧空位附近的电荷分布

Charge Distribution Near Oxygen Vacancies in Reduced Ceria

E. Shoko, M. F. Smith, Ross H. McKenzie

备注：
20 pages, 23 figures. The replacement file has a new format for the figures are the document layout but no change in content. v3 has the following main changes: 1. The abstract and introduction were extensively revised. 2. Sec. IV was removed. 3. The Conclusion was rewritten
发表信息：
J. Phys.: Condens. Matter 22 223201 (2010)
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摘要：

了解过渡金属和稀土氧化物中氧空位周围的电子电荷分布是一项具有相当技术重要性的科学挑战。我们展示了如何显着的信息，在氧化铈中的空位周围的电荷分布可以从研究的高分辨率的晶体结构的高阶氧化物表现出有序的氧空位。具体而言，我们认为Ce $_{7}$ O $_{12}$和Ce $_{11}$ O $_{20}$的键价和分析的影响。为了阐明我们的分析，我们显示了其他代表性的晶体结构方面的有序阵列的协调缺陷，并在碲型模块。我们发现，在Ce $_{7}$ O $_{12}$中，除去氧原子所产生的过量电荷在最靠近O空位的所有三个三斜Ce位点之间离域。在Ce $_{11}$ O $_{20}$中，电荷集中在下一个最近的相邻Ce原子上。我们的主要结果是，电荷倾向于分配自己，使它是最远离O空位。这与\emph{the standard picture of charge localisation}的假设相矛盾，\emph{the standard picture of charge localisation}假设两个过剩电子中的每一个都位于最靠近空位的铈离子之一上。在基于密度泛函理论（DFT）的大多数计算中，都假定了这一标准图像。根据Pr $_{6}$ O $_{11}$的已知晶体结构，我们还预言Ce $_{6}$ O $_{11}$中的电荷将位于O空位的第二配位壳层。虽然这篇评论的重点是散装氧化铈，我们的方法来表征氧空位的电子性质和获得的物理见解也应该是相关的表面缺陷和其他稀土和过渡金属氧化物。

英文摘要：

Understanding the electronic charge distribution around oxygen vacancies in transition metal and rare earth oxides is a scientific challenge of considerable technological importance. We show how significant information about the charge distribution around vacancies in cerium oxide can be gained from a study of high resolution crystal structures of higher order oxides which exhibit ordering of oxygen vacancies. Specifically, we consider the implications of a bond valence sum analysis of Ce$_{7}$O$_{12}$ and Ce$_{11}$O$_{20}$. To illuminate our analysis we show alternative representations of the crystal structures in terms of orderly arrays of co-ordination defects and in terms of flourite-type modules. We found that in Ce$_{7}$O$_{12}$, the excess charge resulting from removal of an oxygen atom delocalizes among all three triclinic Ce sites closest to the O vacancy. In Ce$_{11}$O$_{20}$, the charge localizes on the next nearest neighbour Ce atoms. Our main result is that the charge prefers to distribute itself so that it is farthest away from the O vacancies. This contradicts \emph{the standard picture of charge localisation} which assumes that each of the two excess electrons localises on one of the cerium ions nearest to the vacancy. This standard picture is assumed in most calculations based on density functional theory (DFT). Based on the known crystal structure of Pr$_{6}$O$_{11}$, we also predict that the charge in Ce$_{6}$O$_{11}$ will be found in the second coordination shell of the O vacancy. Although this review focuses on bulk cerium oxides our approach to characterising electronic properties of oxygen vacancies and the physical insights gained should also be relevant to surface defects and to other rare earth and transition metal oxides.

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