Electron density distribution and crystal structure of 21R-AlON, Al7O3N5
Electron density distribution and crystal structure of 21R-AlON, Al7O3N5
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DOI：
10.1017/s0885715613000419
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发表时间：
2013-09-01
影响因子：
0.5
通讯作者：
Fukuda, Koichiro
中科院分区：
文献类型：
--
作者：
Asaka, Toru;Kudo, Tatsunari;Fukuda, Koichiro
Al7O3N5 的晶体结构通过实验室 X 射线粉末衍射 (CuK α(1)) 进行了表征。标题化合物是具有空间群R (3) 的三角晶系（中心对称）。六方晶胞尺寸 (Z = 3) 为 a = 0.305 06(1) nm、c = 5.7216(1) nm 和 V = 0.461 11(2) nm(3)。初始结构模型通过电荷翻转方法推导并通过Rietveld 方法精修。最终的结构模型显示了四个铝位点中两个的位置无序。基于最大熵方法的模式拟合方法被用来确认分裂原子模型的有效性，其中由假设强度划分引起的传统结构偏差被最小化。通过重叠五种具有有序原子排列的域，成功地描述了无序晶体结构。五种类型域之一中原子位置的分布可以在 barm 上的空间群 R (3) 中实现。其他四个域中的原子排列与空间群 R3m 非中心对称。四种域中的两种域通过伪对称反演相关，其余两种域也彼此具有反演伪对称性。 (C) 2013 年国际衍射数据中心。
The crystal structure of Al7O3N5 was characterized by laboratory X-ray powder diffraction (CuK alpha(1)). The title compound is trigonal with a space group R (3) over barm (centrosymmetric). The hexagonal unit-cell dimensions (Z = 3) are a = 0.305 06(1) nm, c = 5.7216(1) nm, and V = 0.461 11(2) nm(3). The initial structural model was derived by the charge-flipping method and refined by the Rietveld method. The final structural model showed the positional disordering of two of the four Al sites. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The disordered crystal structure was successfully described by overlapping five types of domains with ordered atom arrangements. The distribution of atomic positions in one of the five types of domains can be achieved in the space group R (3) over barm. The atom arrangements in the four other domains are non-centrosymmetric with the space group R3m. Two of the four types of domains are related by a pseudo-symmetrical inversion, and the two remaining domains also have each other in the inversion pseudo-symmetry. (C) 2013 International Centre for Diffraction Data.