γ-Al2O3 尖晶石和单斜晶体结构的比较，用于模拟电子能量损失谱,Microscopy and Microanalysis

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γ-Al2O3 尖晶石和单斜晶体结构的比较，用于模拟电子能量损失谱
Microscopy and Microanalysis ( IF 2.9 ) Pub Date : 2017-07-01 , DOI: 10.1017/s1431927617010765
Henry O. Ayoola , Cecile S. Bonifacio , Qing Zhu , Dong Su , Joshua Kas , John J. Rehr , Eric A. Stach , Wissam A. Saidi , Judith C. Yang

γ-Al2O3 是氧化铝的亚稳态多晶型物之一，可用于许多应用，例如吸附剂和催化剂载体 [1]。然而，对γ-Al2O3 晶体结构的准确描述仍存在争议。早期对γ-Al2O3 结构的研究，包括Zhou 和Snyder 的开创性研究[2]，确定γ-Al2O3 具有类似于MgAl2O4 结构的尖晶石结构。由于 γ-Al2O3 每个晶胞中的阳离子比 MgAl2O4 少，一些阳离子位置是空的以满足化学计量。最近，理论研究表明非尖晶石结构是 γ-Al2O3 更准确的结构描述，其中最常被引用的是 Digne 等人。[3]。这些理论家结合分子动力学 (MD) 和密度泛函理论 (DFT) 计算来模拟勃姆石热脱水生成 γ-Al2O3，这是 γ-Al2O3 最常见的合成方法。他们预测γ-Al2O3 结构会扭曲成单斜晶胞。尽管随后的实验研究表明尖晶石模型是更准确的结构描述 [4]，但由于阳离子位点的部分占据，在模拟中使用它的计算量也更大。因此，γ-Al2O3 的单斜模型常用于模拟，包括电子特性的模拟。由于勃姆石脱水产生的 γAl2O3 的性质，测量这种方法的准确性变得复杂，通常表现出较差的结晶度和大量的杂质。

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Comparison of Spinel and Monoclinic Crystal Structures of γ-Al2O3 for Simulation of Electron Energy Loss Spectra

γ-Al2O3 is one of the metastable polymorphs of alumina that is used in many applications, such as in adsorbents and catalyst supports [1]. However, an accurate description of the crystal structure of γ-Al2O3 is still being disputed. Early studies of the structure of γ-Al2O3, including the seminal study by Zhou and Snyder [2], determined γ-Al2O3 has a spinel structure similar to the structure of MgAl2O4. As there are fewer cations in γ-Al2O3 per unit cell than MgAl2O4, some of the cation positions are vacant to satisfy stoichiometry. Recently, theoretical studies have suggested non-spinel structures as the more accurate structural description of γ-Al2O3, the most commonly cited of which was given by Digne et al. [3]. These theorists combined molecular dynamics (MD) and density functional theory (DFT) calculations to simulate the thermal dehydration of boehmite to γ-Al2O3, which is the most common synthesis method of γ-Al2O3. They predicted that the γ-Al2O3 structure was distorted into a monoclinic unit cell. Although subsequent experimental studies suggest that the spinel model is the more accurate structural description [4], it is also more computationally intensive to use in simulations because of the partial occupancy of the cation sites. As a result, the monoclinic model of γ-Al2O3 is commonly used in simulations, including of the electronic properties. Gauging the accuracy of this approach has been complicated by the nature of γAl2O3 produced by the dehydration of boehmite, which usually exhibits poor crystallinity and significant amounts of impurities. This has hindered the ability to directly compare experimental results with simulations, which uses simple, well-defined structures for input.

更新日期：2017-07-01

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