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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Atomic structures of ternary Yb-Cd-Mg icosahedral quasicrystals and a 1/1 approximant
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Atomic structures of ternary Yb-Cd-Mg icosahedral quasicrystals and a 1/1 approximant

机译：三元YB-CD-Mg ICOSAHEDRAL拟rASICSTALS和1/1近似的原子结构

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摘要

Atomic structures of ternary icosahedral (i) Yb-Cd-Mg quasicrystals (QCs) with five different Mg contents up to 46.4 at.% and a corresponding 1/1 approximant (AP), which has a composition of Yb_(13.3)Cd_(70.3)Mg_(16.5), have been analysed by single-crystal X-ray diffraction. The structures of the iQCs were found to be isostructural to the parent i-YbCd_(5.7), which consists of a so-called Tsai-type rhombic triacontahedron (RTH) cluster and double Friauf polyhedron, and that of the 1/1 AP was found to be isostructural to YbCd_6, which is described by a body-centred packing of the same type of RTH cluster. In the iQCs, it was found that there are three types of Cd/Mg occupation, namely, Cd preferential site, Mg preferential site and Cd/Mg mixed site, and the occupation probabilities of Mg atoms at the Mg preferential site show a saturation behaviour around the Mg content of 20 at.%. This selective Mg occupation is identified as a cause of the non-linear increase in the icosahedral lattice constant with increasing Mg content. The 1/1 AP has a similar selective Mg occupation to that of the iQCs in terms of the shell structures of the Tsai-type RTH cluster. In both iQCs and the 1/1 AP, the Mg preferential sites have a smaller number of Yb atoms among their coordination numbers. Moreover, short-range order (s.r.o.) diffuse scattering was observed on the diffraction patterns of the iQCs at the positions corresponding to a face-centred-type (F-type) icosahedral superlattice. The F-type s.r.o. was found to result from the Mg substitution.
机译：三元ICOSAHELAL（I）YB-CD-MG拟rδ（QCS）的原子结构，具有五种不同的Mg含量，高达46.4。％和相应的1/1近似（AP），其具有YB_（13.3）CD_的组成（通过单晶X射线衍射分析了70.3）Mg_（16.5）。发现IQC的结构是对母体I-YBCD_（5.7）的表人视觉，其包括所谓的TSAI型菱形三元珠单体（RTH）簇和双重FRIAUF多面体，以及1/1 AP的群体发现是对YBCD_6的表观，其由相同类型的Rth簇的以体为中心的包装描述。在IQCS中，发现存在三种类型的CD / MG职业，即CD优先网站，Mg优惠部位和Cd / Mg混合位点，并且Mg优惠网站Mg原子的占用概率显示饱和行为围绕mg含量为20。％。这种选择性MG职业被鉴定为ICosaheL晶格常数的非线性增加的原因，随着Mg含量的增加。在TSAI型RTH簇的壳结构方面，1/1AP具有与IQC的类似选择性MG占用。在IQC和1/1 AP中，MG优惠网站在其协调号之间具有较少数量的YB原子。此外，在对应于面为中心型（F型）ICOSAHEDRAL超晶格的位置的IQC的衍射图案上观察到短距离顺序（S.R.O.）漫反射散射。 f型s.r.O.被发现是由MG替换引起的。

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