Structure and Energetics of (111) Surface of γ-Al2O3: Insights from DFT Including Periodic Boundary Approach
Structure and Energetics of (111) Surface of γ-Al2O3: Insights from DFT Including Periodic Boundary Approach
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DOI：
10.1021/acsomega.7b01921
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发表时间：
2018-02-01
期刊：
影响因子：
4.1
通讯作者：
Leszczynski, Jerzy
中科院分区：
文献类型：
--
作者：
Gu, Jiande;Wang, Jing;Leszczynski, Jerzy
对γ -氧化铝的（111）表面进行了重新研究，提出了一种新的（111）表面模型。利用周期边界条件，利用密度泛函和全电子基集对γ -氧化铝（111）(n)表面的局部结构进行了优化。新建立的（111）(n)表面与（110）表面具有相同的稳定性，其表面能为2.561 J/m(2)，仅比（110）表面大约0.002 J/m(2)。在（111）(n)上发现了三种不同类型的三坐标Al中心。分子轨道（MO）分析和居族分析表明，Al(I)是一个非配对电子中心。单占据MO在Al(I)中心的作用有望在γ -氧化铝的催化活性中发挥重要作用。此外，（111）(n)表面邻近的Al（Al(III)）为给电子基团提供了合适的接受位置。发现（111）(n)的缺陷表面具有类似的稳定性。Al(I)脱离（111）(n)表面导致非成对电子中心的消失。同时，Al(I)在（111）(n)表面的附着会在这个新表面上产生丰富的非配对电子中心。因此，这一新定义的表面有望吸引对γ -氧化铝催化活性的研究兴趣。
The (111) surface of gamma-alumina has been reexamined, and a new (111) surface model has been suggested. The local structure of this new surface of gamma-alumina, (111)(n), has been optimized by the density functionals along with the full electron basis sets by using periodic boundary condition. This newly modeled (111)(n) surface is characterized by the same stability as that of the (110) surface, and its surface energy amounts to 2.561 J/m(2), only about 0.002 J/m(2) larger than that of (110). Three different types of the tricoordinated Al centers have been identified on (111)(n). Molecular orbital (MO) analysis and the population analysis demonstrate that one type of Al, Al(I), is a nonpaired electron center. The singly occupied MO on Al(I) center is expected to play an important role in the catalytic activities of the gamma-alumina. Moreover, the neighboring Al (Al(III)) on the (111)(n) surface provides suitable acceptance position for the electron donating groups. The defected surfaces of (111)(n) are found to be having a similar stability. The detachment of Al(I) from the (111)(n) surface results in disappearance of the nonpaired electron centers. Meanwhile, the attachment of Al(I) on (111)(n) surface will produce rich nonpaired electron centers on this new surface. Therefore, this newly defined surface is expected to attract the research interests in the catalytic activities of gamma-alumina.