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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Structure refinement of the layered composite crystal Sc2B1.1C3.2 in a five-dimensional formalism.
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Structure refinement of the layered composite crystal Sc2B1.1C3.2 in a five-dimensional formalism.

机译：层状复合晶体Sc2B1.1C3.2的五维形式结构精细化。

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摘要

The crystal structure of a layered compound Sc(2)B(1.1)C(3.2), scandium boride carbide (M(r) = 140.43), has been re-refined as a commensurate composite crystal using 1795 single-crystal X-ray diffraction intensities with I > 2 sigma(I) collected by Shi, Leithe-Jasper, Bourgeois, Bando & Tanaka [(1999), J. Solid State Chem. 148, 442--449]. The crystal is composed of two layered subsystem structures, i.e. Sc--C--Sc sandwiches and graphite-like layers of the composition B(1/3)C(2/3). The structure refinement was performed in a five-dimensional formalism based on the trigonal superspace group P3m1(p00)(0p0)0m0. The unit cell and other crystal data are a = b = 3.387 (1), c = 6.703 (2) A, V = 66.59 (1) A(3), sigma(1) = (9/7 0 0), sigma(2) = (0 9/7 0), Z = 1, D(x) = 3.501 Mg m(-3). Two different three-dimensional sections through the superspace were analyzed, corresponding to two different superstructure models, one with P3m1 and the other with P3m1. A random distribution of B and C was assumed in the graphite-like layer and 41 structural parameters were introduced. R(F)/wR(F) were 0.0533/0.0482 and 0.0524/0.0476, respectively, for the first and second models. Although the difference between these R(F) or wR(F) values was too fine to exclude one of the models definitely, the advantages of using a superspace group were obvious. It not only brought about better convergence of refinement cycles by virtue of fewer parameters, but also gave an insight into the problem of symmetry of the superstructure.
机译：层状化合物Sc（2）B（1.1）C（3.2）的晶体结构，碳化carbide碳化硼（M（r）= 140.43），已使用1795年单晶X射线重新精炼为相应的复合晶体。由Shi，Leethe-Jasper，Bourgeois，Bando和Tanaka收集的I> 2 sigma（I）的衍射强度[（1999），J。 148，442--449]。晶体由两层子系统结构组成，即Sc--C--Sc三明治和B（1/3）C（2/3）组成的类石墨层。基于三角超空间组P3m1（p00）（0p0）0m0，以五维形式主义对结构进行细化。晶胞和其他晶体数据为a = b = 3.387（1），c = 6.703（2）A，V = 66.59（1）A（3），sigma（1）=（9/7 0 0），sigma （2）=（0 9/7 0），Z = 1，D（x）= 3.501 Mg m（-3）。分析了通过超空间的两个不同的三维截面，对应于两个不同的上层建筑模型，一个具有P3m1，另一个具有P3m1。假设在石墨状层中B和C的随机分布，并引入了41个结构参数。对于第一和第二个模型，R（F）/ wR（F）分别为0.0533 / 0.0482和0.0524 / 0.0476。尽管这些R（F）或wR（F）值之间的差异太小，无法明确排除其中一个模型，但使用超空间组的优势显而易见。它不仅可以通过减少参数来实现细化循环的更好收敛，而且可以洞悉上部结构的对称性问题。

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