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Geometric Analysis and Formability of the Cubic A2BX6 Vacancy-Ordered Double Perovskite Structure
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-11-04 , DOI: 10.1021/acs.chemmater.0c02806
Warda Rahim 1, 2 , Anjie Cheng 1 , Chenyang Lyu 1 , Tianyi Shi 1 , Ziheng Wang 1 , David O. Scanlon 1, 2, 3 , Robert G. Palgrave 1
Affiliation  

A geometric analysis of the cubic A2BX6 structure commonly formed by metal halides is presented. Using the “hard-sphere” approximation, where the ions are represented by spheres of a fixed radius, we derive four limiting models that each constrain the distances between constituent ions in different ways. We compare the lattice parameters predicted by these four models with experimental data from the Inorganic Crystal Structure Database (ICSD). For the fluorides, the maintenance of the AX bond length at the sum of the A and X radii gives the best approximation of the lattice parameter, leading to structures with widely separated BX6 octahedra. For the heavier halides, a balance between forming an A-site cavity of the correct size and maintaining suitable anion–anion distances determines the lattice parameter. It is found that in many A2BX6 compounds of heavier halides, the neighboring octahedra show very significant anion–anion overlap. We use these models to predict a compound with A-site rattling and use density functional theory (DFT) to confirm this prediction. Finally, we use the geometric models to derive formability criteria for vacancy-ordered double perovskites.

中文翻译:

立方A 2 BX 6空位有序双钙钛矿结构的几何分析和可成形性

介绍了通常由金属卤化物形成的立方A 2 BX 6结构的几何分析。使用“硬球”近似法(其中离子由固定半径的球体表示),我们导出了四个限制模型,每个模型以不同的方式约束组成离子之间的距离。我们将这四个模型预测的晶格参数与无机晶体结构数据库(ICSD)的实验数据进行了比较。对于氟化物,将AX键长度保持在A和X半径的总和可提供最佳的晶格参数近似值,从而导致结构与BX 6广泛分离八面体。对于较重的卤化物,在形成正确尺寸的A位置腔和保持合适的阴离子-阴离子距离之间的平衡决定了晶格参数。已发现在许多重卤化物的A 2 BX 6化合物中,相邻的八面体显示出非常显着的阴离子-阴离子重叠。我们使用这些模型来预测具有A位咔嗒声的化合物,并使用密度泛函理论(DFT)确认该预测。最后,我们使用几何模型来得出空缺有序双钙钛矿的可成形性标准。
更新日期:2020-11-25
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