Fabris Stefano, Vicario Gianpaolo, Balducci Gabriele, de Gironcoli Stefano, Baroni Stefano
INFM-CNR DEMOCRITOS National Simulation Center and Scuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34014 Trieste, Italy.
J Phys Chem B. 2005 Dec 8;109(48):22860-7. doi: 10.1021/jp0511698.
The atomistic and electronic structures of oxygen vacancies on the (111) and (110) surfaces of ceria are studied by means of periodic density functional calculations. The removal of a neutral surface oxygen atom leaves back two excess electrons that are shown to localize on two cerium ions neighboring the defect. The resulting change of valency of these Ce ions (Ce4+ --> Ce3+) originates from populating tightly bound Ce 4f states and is modeled by adding a Hubbard U term to the traditional energy functionals. The calculated atomistic and electronic structures of the defect-free and reduced surfaces are shown to agree with spectroscopic and microscopic measurements. The preferential defect segregation and the different chemical reactivity of the (111) and (110) surfaces are discussed in terms of energetics and features in the electronic structure.
通过周期性密度泛函计算研究了二氧化铈（111）和（110）表面氧空位的原子结构和电子结构。去除一个中性表面氧原子会留下两个多余电子，这些电子显示定域在缺陷附近的两个铈离子上。这些铈离子（Ce4+→Ce3+）价态的变化源于填充紧密束缚的Ce 4f态，并通过在传统能量泛函中添加哈伯德U项来模拟。计算得到的无缺陷和还原表面的原子结构和电子结构与光谱和显微镜测量结果相符。从能量学和电子结构特征方面讨论了（111）和（110）表面优先的缺陷偏析和不同的化学反应性。
