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The atomic structure of the Bergman-type icosahedral quasicrystal based on the Ammann-Kramer-Neri tiling.
Acta Crystallographica Section A: Foundations and Advances ( IF 1.9 ) Pub Date : 2020-02-11 , DOI: 10.1107/s2053273319017339
Ireneusz Buganski 1 , Janusz Wolny 1 , Hiroyuki Takakura 2
Affiliation  

In this study, the atomic structure of the ternary icosahedral ZnMgTm quasicrystal (QC) is investigated by means of single-crystal X-ray diffraction. The structure is found to be a member of the Bergman QC family, frequently found in Zn-Mg-rare-earth systems. The ab initio structure solution was obtained by the use of the Superflip software. The infinite structure model was founded on the atomic decoration of two golden rhombohedra, with an edge length of 21.7 Å, constituting the Ammann-Kramer-Neri tiling. The refined structure converged well with the experimental diffraction diagram, with the crystallographic R factor equal to 9.8%. The Bergman clusters were found to be bonded by four possible linkages. Only two linkages, b and c, are detected in approximant crystals and are employed to model the icosahedral QCs in the cluster approach known for the CdYb Tsai-type QC. Additional short b and a linkages are found in this study. Short interatomic distances are not generated by those linkages due to the systematic absence of atoms and the formation of split atomic positions. The presence of four linkages allows the structure to be pictured as a complete covering by rhombic triacontahedral clusters and consequently there is no need to define the interstitial part of the structure (i.e. that outside the cluster). The 6D embedding of the solved structure is discussed for the final verification of the model.

中文翻译:


基于 Ammann-Kramer-Neri 平铺的 Bergman 型二十面体准晶的原子结构。



在这项研究中,通过单晶X射线衍射研究了三元二十面体ZnMgTm准晶(QC)的原子结构。该结构被发现是 Bergman QC 家族的成员,常见于 Zn-Mg-稀土系统中。利用Superflip软件得到从头算结构解。无限结构模型建立在两个边长为 21.7 Å 的金色菱面体的原子装饰之上,构成 Ammann-Kramer-Neri 平铺。细化后的结构与实验衍射图收敛良好,晶体学R因子等于9.8%。伯格曼簇被发现由四种可能的联系连接在一起。在近似晶体中仅检测到两个键 b 和 c,并用于在 CdYb Tsai 型 QC 已知的簇方法中对二十面体 QC 进行建模。本研究中发现了额外的短 b 和 a 连接。由于原子的系统缺失和分裂原子位置的形成,这些连接不会产生较短的原子间距离。四个连接的存在使得该结构可以被描绘为菱形三十面体簇的完全覆盖,因此不需要定义该结构的间隙部分(即簇之外的间隙部分)。讨论了已求解结构​​的 6D 嵌入,以进行模型的最终验证。
更新日期:2020-02-11
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