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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Polytypism of LiSr_2Ge_3 and the solid solutions LiSr_2Si_xGe_(3-x) and LiSr_(2-x)Eu _xGe_3 (0 < x < 1)
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Polytypism of LiSr_2Ge_3 and the solid solutions LiSr_2Si_xGe_(3-x) and LiSr_(2-x)Eu _xGe_3 (0 < x < 1)

机译：LiSr_2Ge_3和固溶体LiSr_2Si_xGe_（3-x）和LiSr_（2-x）Eu _xGe_3（0

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Three modifications of LiSr_2Ge_3 were prepared by solid state syntheses at high temperatures under inert conditions in sealed niobium ampoules. α-LiSr_2Ge_3 [space group Pnnm (No. 58), a = 11.102(1), b = 11.862(1), c = 4.631(1) ?, Z = 2] is isostructural to LiCa_2Tt_3 (Tt = Si, Ge), containing a one-dimensional infinite germanium chain in (tttctc)n conformation. β-LiSr _2Ge_3 [space group Fmmm (No. 69), a = 8.733(1), b = 8.996(1), c = 15.045(2) ?, Z = 4] crystallizes with the AgCa _2Si_3 structure. The β-phase shows a tendency for lithium deficiency, which may be as small as 6 % but can be larger. γ-LiSr_2Ge_3 [space group Fddd (No. 70), a = 8.675(3), b = 15.066(5), c = 18.258(5) ?, Z = 8] is isostructural to LiBa _2Tt_3. The latter two structures contain planar and distorted Ge6-rings, respectively. Comparison of the structures reveals significant changes of lattice parameters and bond lengths. β-LiSr_2Ge_3 may be stabilized by a slightly smaller lithium content due to preparation procedure. This assumption is supported by the structure analysis and total energy calculations. LiSr_2Ge _3 can be formulated as (Li~+)_2(Sr ~(2+))_4[Ge_6]~(10-) according to the Zintl-Klemm concept, with each of the Zintl anions having a partially occupied delocalized π* system. Theoretical investigations indicate metallic properties since π* bands are crossing the Fermi level. Phase widths were explored for Ge/Si and Sr/Eu exchange and complete miscibility was found for both series. Mixed silicide germanides exclusively crystallize in form of the γ-phase, whereas the Eu-containing mixed phases prefer the α-form, both throughout the series.
机译：LiSr_2Ge_3的三种修饰形式是在密封的铌安瓿瓶中，在惰性条件下，在高温下通过固态合成制备的。 α-LiSr_2Ge_3[空间群Pnnm（No. 58），a = 11.102（1），b = 11.862（1），c = 4.631（1）？，Z = 2]与LiCa_2Tt_3（Tt = Si，Ge）同构，其中包含（tttctc）n构型的一维无限锗链。 β-LiSr_2Ge_3 [空间群Fmmm（No. 69），a = 8.733（1），b = 8.996（1），c = 15.045（2）α，Z = 4]用AgCa _2Si_3结构结晶。 β相显示出锂缺乏的趋势，其可能小至6％但可以更大。 γ-LiSr_2Ge_3[空间群Fddd（No.70），a ＝ 8.675（3），b ＝ 15.066（5），c ＝ 18.258（5）≤，Z ＝ 8]与LiBa_2Tt_3同构。后两个结构分别包含平面的和扭曲的Ge6-环。结构的比较显示出晶格参数和键长的显着变化。由于制备步骤，β-LiSr_2Ge_3可以通过稍微小的锂含量来稳定。该假设得到结构分析和总能量计算的支持。根据Zintl-Klemm概念，可以将LiSr_2Ge _3表示为（Li〜+）_ 2（Sr〜（2 +））_ 4 [Ge_6]〜（10-），每个Zintl阴离子都具有部分占据的离域π*系统。理论研究表明，由于π*谱带越过费米能级，因此具有金属特性。探索了Ge / Si和Sr / Eu交换的相宽，发现两个系列都具有完全的混溶性。在整个系列中，混合的硅化物锗化物仅以γ相形式结晶，而含Eu的混合相则更倾向于α形式。

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