Lin Qisheng, Corbett John D
Department of Chemistry, Iowa State University, Ames, 50011, USA.
J Am Chem Soc. 2006 Oct 11;128(40):13268-73. doi: 10.1021/ja063897u.
Single-crystal structures are reported for Sc(3)Mg(0.18(1))Zn(17.73(3)), the 1/1 approximant crystal (AC), and Sc(11.18(9))Mg(2.5(1))Zn(73.6(2)), the 2/1 AC, in the corresponding icosahedral quasicrystal (i-QC) system. The 1/1 AC crystallizes in space group Im, a = 13.863(2) A, Z = 8, and the 2/1 AC, in Pa, a = 22.412 (2) A, Z = 8. The latter, which is valuable in pointing the way to the QC structure, is the best ordered and refined 2/1 example to date. The fundamental building blocks in both ACs are triacontahedral clusters centered by smaller multiply endohedral Tsai-type arrays; the former are condensed through body-centered-cubic packing in the 1/1 and primitive cubic packing in the 2/1 AC. Novel prolate rhombohedra centered by Sc-Sc dimers are also generated between triacontahedra in the 2/1 AC.
报道了Sc(3)Mg(0.18(1))Zn(17.73(3))（1/1近似晶体（AC））和Sc(11.18(9))Mg(2.5(1))Zn(73.6(2))（2/1 AC）在相应二十面体准晶体（i-QC）体系中的单晶结构。1/1 AC属于空间群Im，a = 13.863(2) Å，Z = 8；2/1 AC属于空间群Pa，a = 22.412 (2) Å，Z = 8。后者对于指明准晶体结构的方向很有价值，是迄今为止有序度最好且精修的2/1实例。两种AC中的基本结构单元都是以较小的多重内包蔡氏型阵列作为中心的三十面体簇；前者在1/1 AC中通过体心立方堆积凝聚，在2/1 AC中通过简单立方堆积凝聚。在2/1 AC的三十面体之间还生成了以Sc-Sc二聚体为中心的新型长菱面体。
