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首页> 外文期刊>Chemistry: A European journal >Ta_(97)Te_(60):A Crystalline Approximant of a Tantalum Telluride Quasicrystal with Twelvefold Rotational Symmetry
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Ta_(97)Te_(60):A Crystalline Approximant of a Tantalum Telluride Quasicrystal with Twelvefold Rotational Symmetry

机译：Ta_（97）Te_（60）：具有十二倍旋转对称性的碲化钽准晶体的晶体近似

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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 Ta_(97)Ta_(60) 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_1P2_12_1, Pearson symbol Op628, 1415 variables, R(F) = 0.059. A dodecagonal-shaped, vaulted Ta_(151)Te_(74) cluster with maximum symmetry 6mm can be seen as a characteristic motif of the structure. Each clsuter measures about 2.5 nm across and consists of nineteen concentrically condensed hexagonal antiprismatic Ta_(13) clusters which are capped with Te atoms. The Ta_(151)Te_(74) clusters can cover the plane distinctly in different ways, thereby forming a series of phases which are closely related both structurally and compositionally. In Ta_(97)Te_(60) the buckled clusters decorate the vertices of a square tiling at a 2nm length scale to result in corrugated lamellae _(infinity)~2[Te_(30)Ta_(41)Ta_(15~-)Ta_(41)Te_(30)] each about 1 nm thick. The lamellae are stacked along the c axis, corresponding to the direction of the pseudo-twelvefold 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 and a doubling of the staking vector c.
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Ta_（97）Ta_（60）的原子排列已通过30458对称独立的X射线强度确定，该强度由度量美因学孪晶而成：a = 2767.2（2），b = 2767.2（2）， c = 2061.3（2）pm，空间组P2_1P2_12_1，Pearson符号Op628，1415个变量，R（F）= 0.059。具有最大对称性6mm的十二边形拱形Ta_（151）Te_（74）团簇可以看作是该结构的特征性图案。每个丛的大小约为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。 Ta_（151）Te_（74）团簇可以以不同的方式清楚地覆盖平面，从而形成一系列在结构和成分上密切相关的相。在Ta_（97）Te_（60）中，弯曲的簇以2nm的长度尺度装饰正方形平铺的顶点，从而产生波纹薄片_（infinity）〜2 [Te_（30）Ta_（41）Ta_（15〜-） Ta_（41）Te_（30）]各自约1nm厚。薄片沿着c轴堆叠，该c轴对应于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层间Te-Te相互作用的微调有关，这反映在与平均距离的偏差最小化和放样向量c。

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