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首页> 外文期刊>Chemistry: A European journal >Ta97Te60: A crystalline approximant of a tantalum telluride quasicrystal with twelvefold rotational symmetry
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Ta97Te60: A crystalline approximant of a tantalum telluride quasicrystal with twelvefold rotational symmetry

机译：Ta97Te60：具有十二倍旋转对称性的碲化钽准晶体的晶体近似物

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摘要

The crystal structure of a rational approximant of an unprecedented dodecagonal quasicrystal is reported. The atomic arrangement of the tantalum-rich telluride Ta97Te60 has been determined from 30458 symmetrically independent X-ray intensities of a crystal twinned by metric merohedry: a = 2767.2(2), b = 2767.2(2), c = 2061.3(2) pm, space group P2(1)2(1)2(1), Pearson symbol oP628, 1415 variables, R(F) = 0.059. A dodecagonal-shaped, vaulted Ta151Te74 cluster with maximum symmetry 6mm can be seen as a characteristic motif of the structure. Each cluster measures about 2.5 nm across and consists of nineteen concentrically condensed hexagonal antiprismatic Ta-13 clusters which are capped with Te atoms. The Ta151Te74 clusters can cover the plane distinctly in different ways, thereby forming a series of phases which are closely related both structurally and compositionally. In Ta97Te60 the buckled clusters decorate the vertices of a square tiling at a 2 nm length scale to result in corrugated lamellae (2)(infinity)[Te30Ta41Ta15Ta41Te30] each about 1 nm thick. The lamellae are stacked along the c axis, corresponding to the direction of the b pseudo-twelve fold axis of symmetry. Symmetry arguments are proposed that the twinning of the structure may be associated with a fine-tuning of weak interlayer Te - Te interactions which are reflected in a minimization of the deviation from the mean distance [d(Te-Te)] and a doubling, of the stacking vector c. [References: 60]
机译：报道了前所未有的十二边形准晶体的有理近似的晶体结构。富钽碲化物Ta97Te60的原子排列是通过以对称金属光度学孪晶的30458对称对称X射线强度确定的：a = 2767.2（2），b = 2767.2（2），c = 2061.3（2）pm ，空间组P2（1）2（1）2（1），Pearson符号oP628、1415个变量，R（F）= 0.059。具有最大对称性为6mm的十二边形拱形Ta151Te74簇可以看作是该结构的特征性图案。每个簇的长度约为2.5 nm，由19个同心稠密的六角反棱形Ta-13簇组成，这些簇被Te原子封端。 Ta151Te74团簇可以以不同的方式明显覆盖平面，从而形成一系列在结构和组成上都密切相关的相。在Ta97Te60中，弯曲的簇以2 nm的长度尺度装饰正方形平铺的顶点，从而产生波纹薄片（2）（无限大）[Te30Ta41Ta15Ta41Te30]，每个薄片的厚度约为1 nm。薄片沿着c轴堆叠，该c轴对应于b拟十二折对称轴的方向。提出了对称性论证，即结构的孪晶可能与微弱的中间层Te-Te相互作用的微调有关，这反映在与平均距离[d（Te-Te）]的偏差最小和加倍的情况下，堆叠向量c。 [参考：60]

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