Makongo Julien P A, Bobev Svilen
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
Acta Crystallogr C Struct Chem. 2014 Jan;70(Pt 1):2-6. doi: 10.1107/S2053229613029604. Epub 2013 Dec 7.
The series of RE5Li2Sn7 (RE = Ce-Sm) compounds were synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. The compounds are pentacerium dilithium heptastannide, Ce5Li1.97Sn7.03, pentapreseodymium dilithium heptastannide, Pr5Li1.98Sn7.02, pentaneodymium dilithium heptastannide, Nd5Li1.99Sn7.01, and pentasamarium dilithium heptastannide, Sm5Li2Sn7. All five compounds crystallize in the chiral orthorhombic space group P212121 (No. 19), which is relatively uncommon among intermetallic phases. The structure belongs to the Ce5Li2Sn7 structure type (Pearson symbol oP56), with 14 unique atoms in the asymmetric unit. Minor compositional variations exist, due to the mixed occupancy of Li and Sn atoms at one of the Li sites. The small occupational disorder is most evident for RE5Li2-xSn7+x (RE = Ce, Pr; x ≃ 0.03), while the structure of Nd5Li2Sn7 and Sm5Li2Sn7 show no apparent disorder.
通过高温反应合成了一系列RE5Li2Sn7（RE = Ce - Sm）化合物，并通过单晶X射线衍射对其结构进行了表征。这些化合物分别是五铈二锂七锡化物Ce5Li1.97Sn7.03、五镨二锂七锡化物Pr5Li1.98Sn7.02、五钕二锂七锡化物Nd5Li1.99Sn7.01和五钐二锂七锡化物Sm5Li2Sn7。所有这五种化合物都结晶在手性正交空间群P212121（编号19）中，这在金属间相里相对不常见。该结构属于Ce5Li2Sn7结构类型（皮尔逊符号oP56），不对称单元中有14个独特原子。由于Li和Sn原子在一个Li位点上的混合占据，存在微小的成分变化。这种小的占位无序对于RE5Li2 - xSn7 + x（RE = Ce，Pr；x ≃ 0.03）最为明显，而Nd5Li2Sn7和Sm5Li2Sn7的结构没有明显的无序。
