Calcium Substitution in Rare‐earth Metal Germanides with the Gd 5 Si 4 Type Structure
Calcium Substitution in Rare‐earth Metal Germanides with the Gd 5 Si 4 Type Structure
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具有 Gd 5 Si 4 型结构的稀土金属锗化物中的钙替代
DOI：
10.1002/zaac.202200016
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Bobev, Svilen
中科院分区：
文献类型：
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作者：
Suen, Nian‐Tzu;Bobev, Svilen
一系列稀土金属钙锗化物已被合成并进行了结构表征。该化合物具有通式RE5−xCaxGe4（1.5<x<3.6；RE=稀土金属；Ce、Nd、Sm、Tb−Lu），其结构已通过单晶X射线衍射方法确定。它们在正交空间群 Pnma（No. 62；Z=4；Pearson 符号 P36）中以 Gd5Si4 型结晶，其中锗原子互连成两种 Ge2 二聚体，形式为 [Ge2]6−。这些研究表明，Ca 可以成功地结合到主体 RE5Ge4 结构中，从而三价稀土金属原子可以被二价钙原子取代。稀土金属和钙原子排列成扭曲的三棱柱和立方体，以Ge或Ca原子为中心。在其中一个金属位点上，取代是优先的，并且在 10 个精炼结构中的 9 个中，发现威科夫位点 4cis 几乎完全被 Ca 占据。在另外两个金属位点上，取代模式似乎受RE3+和Ca2+离子大小之间的不匹配的控制。这项工作进一步证明了 Gd5Si4 结构类型能够适应非磁性元素的替代，同时保持整体结构完整性。
An extended series of rare‐earth metal calcium germanides have been synthesized and structurally characterized. The compounds have the general formulaRE5−xCaxGe4(1.5<x<3.6;RE=rare‐earth metal; Ce, Nd, Sm, Tb−Lu) and their structures have been established from single‐crystal X‐ray diffraction methods. They crystallize with the Gd5Si4‐type in the orthorhombic space groupPnma(No. 62;Z=4; Pearson symboloP36), where the germanium atoms are interconnected into two kinds of Ge2‐dimers, formally [Ge2]6−. These studies show that Ca can be successfully incorporated into the hostRE5Ge4structure, whereby trivalent rare‐earth metal atoms can be substituted by divalent calcium atoms. Rare‐earth metal and calcium atoms are arranged in distorted trigonal prisms and cubes, centered by either Ge or Ca atoms. On one of the metal sites, the substitution is preferential and in 9 out of the 10 refined structures, the Wyckoff site 4cis found almost exclusively occupied by Ca. On the other two metal sites the substitution patterns appear to be governed by the mismatch between the size of theRE3+and Ca2+ions. This work further demonstrates the ability for the Gd5Si4structure type to accommodate the substitution of a non‐magnetic element while maintaining the global structural integrity.