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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Cobalt centered trigonal RE6 prisms and Mg-4 clusters as basic structural units in RE4CoMg (RE = Y, La, Pr, Nd, Sm, Gd-Tm)
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Cobalt centered trigonal RE6 prisms and Mg-4 clusters as basic structural units in RE4CoMg (RE = Y, La, Pr, Nd, Sm, Gd-Tm)

机译：以钴为中心的三角RE6棱镜和Mg-4簇作为RE4CoMg中的基本结构单元（RE = Y，La，Pr，Nd，Sm，Gd-Tm）

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摘要

The new rare earth metal rich intermetallic compounds RE4CoMg (RE = Y. La, Pr, Nd, Sm, Gd-Tm) were prepared via melting of the elements in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. The compounds were investigated by X-ray diffraction of powders and single crystals: Gd4RhIn type, F43m, a = 1428.38(9) pm, wR2 = 0.0638, 680 F-2 values, 20 variables for La4COMg, a = 1399.5(2) pm, wR2 = 0.0584, 589 F-2 values, 20 variables for Pr4CoMg, a = 1390.2(3) pm, wR2 = 0.0513, 634 F-2 values, 20 variables for Nd3.90CoMg1.10, a 1381.0(3) pm. wR2 = 0.0730, 618 F-2 values, 22 variables for Sm3.92Co0.93Mg1.08, a = 1373.1(4) pm, wR2 = 0.0586, 611 F-2 values, 20 variables for Gd3.92CoMg1.08, a = 1362.1(3) pm, wR2 = 0.0576, 590 F-2 values, 20 variables for Tb3.77CoMg1.23, a = 1344.8(2)pm, wR2 = 0.0683, 511 F-2 values, 20 variables for Dy3.27CoMg1.73, and a = 1343.3(2)pm, wR2 = 0.0560, 542 F-2 values, 20 variables for Er3.72CoMg1.28. The cobalt atoms have trigonal prismatic rare earth coordination. Condensation of the CoRE6 prisms leads to a three-dimensional network which leaves larger voids that are filled by regular Mg-4 tetrahedra at a Mg-Mg distance of 316 pm in La4COMg. The magnesium atoms have twelve nearest neighbors (3 Mg + 9 RE) in icosahedral coordination. In the structures with Nd, Sm, Gd, Tb, Dy, and Er, the REI positions which are not involved in the trigonal prismatic network reveal some RE1/Mg mixing and the Sm3.92Co0.93Mg1.08 structure shows small cobalt defects. Considering La4COMg as representative of all studied systems an analysis of the chemical bonding within density functional theory closely reproduces the crystal chemistry scheme and shows the role played by the valence states of the different constituents in the electronic band structure. Strong bonding interactions were observed between the lanthanum and cobalt atoms within the trigonal prismatic network.
机译：在高频炉水冷样品室中，通过密封钽管中元素的熔化，制备了新型的富含稀土金属的金属间化合物RE4CoMg（RE = Y. La，Pr，Nd，Sm，Gd-Tm）。 。通过粉末和单晶的X射线衍射研究了这些化合物：Gd4RhIn型，F43m，a = 1428.38（9）pm，wR2 = 0.0638，680 F-2值，La4COMg的20个变量，a = 1399.5（2）pm ，wR2 = 0.0584，589个F-2值，Pr4CoMg的20个变量，a = 1390.2（3）pm，wR2 = 0.0513，634 F-2值，Nd3.90CoMg1.10的20个变量，1381.0（3）pm。 wR2 = 0.0730，618个F-2值，Sm3.92Co0.93Mg1.08的22个变量，a = 1373.1（4）pm，wR2 = 0.0586，611个F-2值，Gd3.92CoMg1.08的20个变量，a = 1362.1（3）pm，wR2 = 0.0576，590 F-2值，Tb3.77CoMg1.23的20个变量，a = 1344.8（2）pm，wR2 = 0.0683，511 F-2值，Dy3.27CoMg1的20个变量。 73，a = 1343.3（2）pm，wR2 = 0.0560，542 F-2值，Er3.72CoMg1.28的20个变量。钴原子具有三角棱柱形稀土配位。 CoRE6棱镜的凝结导致形成三维网络，该三维网络留下较大的空隙，这些空隙由La4COMg中Mg-Mg距离为316 pm的规则Mg-4四面体填充。镁原子在二十面体配位中具有十二个最近的邻居（3 Mg + 9 RE）。在具有Nd，Sm，Gd，Tb，Dy和Er的结构中，不参与三角棱柱网络的REI位置显示出一些RE1 / Mg混合，而Sm3.92Co0.93Mg1.08结构显示出较小的钴缺陷。考虑到La4COMg是所有研究系统的代表，在密度泛函理论内对化学键的分析紧密地再现了晶体化学方案，并显示了电子带结构中不同成分的价态所起的作用。在三角棱柱网络中观察到镧和钴原子之间的强键相互作用。

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