ABSTRACT The superstructure and basic structure of ternary Yb-Cd-Mg 1/1 quasicrystal approximants with the compositions Yb Cd Mg and Yb Cd Mg were investigated using X-ray structural analysis. The former was determined to have a face-centred packing structure comprising two distinguishable Tsai-type rhombic triacontahedron clusters (space group , Å), while the latter was found to have a body-centred packing structure made of identical Tsai-type rhombic triacontahedron clusters (space group , Å). The distinction between the two types of clusters in the superstructure is based on the positional disorder of the first tetrahedron shell and the relative Cd/Mg occupancy at M5 sites in the fourth icosidodecahedron shell. In both the superstructure and basic structure, sites preferentially occupied by Mg typically have two Yb atoms among the atoms to which they are coordinated. Finally, a six-dimensional structural model of the primitive Tsai-type icosahedral quasicrystals was modified so as to incorporate the selective Cd/Mg occupation found in the 1/1 approximants.

中文翻译：

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三元 Yb-Cd-Mg 1/1 准晶中超结构的形成

摘要 利用 X 射线结构分析研究了成分为 Yb Cd Mg 和 Yb Cd Mg 的三元 Yb-Cd-Mg 1/1 准晶近似物的超结构和基本结构。前者被确定具有面心堆积结构，包括两个可区分的 Tsai 型菱形三十面体簇（空间群，Å），而后者被发现具有体心堆积结构，由相同的 Tsai 型菱形十三面体簇组成（空间群，Å）。上层结构中两类簇的区别是基于第一四面体壳的位置无序和第四二十面体壳中 M5 位点的相对 Cd/Mg 占有率。在上层建筑和基础结构中，Mg 优先占据的位置通常在它们配位的原子中具有两个 Yb 原子。最后，对原始 Tsai 型二十面体准晶的六维结构模型进行了修改，以纳入在 1/1 近似值中发现的选择性 Cd/Mg 占据。