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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >New ternary boride carbides RE_(10)B_(9+x)C_(10-x) (RE = Gd, Tb; x ≈ 0.2): Infinite boron carbon branched chains
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New ternary boride carbides RE_(10)B_(9+x)C_(10-x) (RE = Gd, Tb; x ≈ 0.2): Infinite boron carbon branched chains

机译:新的三元碳化硼RE_(10)B_(9 + x)C_(10-x)(RE = Gd,Tb; x≈0.2):无限硼碳支链

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摘要

New ternary rare earth metal boride carbides with compositions close to RE_(10)B_9C_(10) (RE = Gd, Tb) were prepared from the elements by melting around 1800 K followed by annealing in silica tubes at 1270 K for one month, The crystal structure of the terbium compound was solved by single-crystal X-ray diffraction. It crystallizes in a new structure type in the monoclinic space group P2_(1/c), a = 7.937(1), b = 23.786(2), c = 11.172(1) ?, ? = 133.74(1)°, Z = 4, R1 = 0.045 (wRl = 0.11) for 5713 reflections with Io > 2σ(I_O) In the structure BC _2 units and single carbon atoms are attached to a zigzag boron chain forming the unprecedented B_(18)C_(18) branching unit with a B-B distance of 2,42(2) ? between these units. In addition isolated carbon atoms occupy the centres of elongated octahedra formed by rare earth metal. atoms. Disorder in the terbium position together with anomalous displacement ellipsoids for carbon atoms except of those in the BC_2 fragments can be rationalized in terms of a slight deviation in stoichiometry, Tb _(10)B_(9+x)C_(10-x)(x ≈ 0.2). The terbium compound is ferromagnetic below T_c≈ 45 K. Due to the presence of moderately narrow domain walls the magneto-crystalline energy is small.
机译:由元素制备新的三元稀土金属硼化物碳化物,其成分接近RE_(10)B_9C_(10)(RE = Gd,Tb),方法是在1800 K左右熔化后在1270 K的石英管中退火一个月, single化合物的晶体结构通过单晶X射线衍射解析。它在单斜空间群P2_(1 / c)中以新的结构类型结晶,a = 7.937(1),b = 23.786(2),c = 11.172(1)?,? = 133.74(1)°,Z = 4,对于Io>2σ(I_O)的5713次反射,R1 = 0.045(wRl = 0.11)在结构BC _2中,单个碳原子与之字形硼链相连,形成空前的B_ (18)C_(18)分支单元的BB距离为2,42(2)?在这些单位之间。另外,孤立的碳原子占据了由稀土金属形成的细长八面体的中心。原子。位置的紊乱以及除BC_2片段中的碳原子以外的碳原子的异常位移椭球可以根据化学计量的微小偏差Tb _(10)B_(9 + x)C_(10-x)( x≈0.2)。 T化合物在T_c≈45K以下具有铁磁性。由于存在适度狭窄的畴壁,因此磁晶能很小。

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