Tobash Paul H, DiFilippo Gary, Bobev Svilen, Hur Namjung, Thompson Joe D, Sarrao John L
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Inorg Chem. 2007 Oct 15;46(21):8690-7. doi: 10.1021/ic7009034. Epub 2007 Sep 18.
The new binary compound Gd(3)Ge(4) has been synthesized and its structure has been determined from single-crystal X-ray diffraction. Gd(3)Ge(4) crystallizes in the orthorhombic space group Cmcm (No. 63) with unit cell parameters a = 4.0953(11) A, b = 10.735(3) A, c = 14.335(4) A, and Z = 4. Its structure can be described as corrugated layers of germanium atoms with gadolinium atoms enclosed between them. The bonding arrangement in Gd(3)Ge(4) can also be derived from that of the known compound GdGe (CrB type) through cleavage of the (infinity)(1)[Ge(2)] zigzag chains in GdGe and a subsequent insertion of an extra germanium atom between the resulting triangular fragments. Formally, these characteristics represent isotypism with the Er(3)Ge(4) type (Pearson's oC28). However, re-examination of the crystallography in the whole RE(3)Ge(4) series (RE = Y, Tb-Tm) revealed discrepancies and called into question the accuracy of the originally determined structures. This necessitated a new rationalization of the bonding, which is provided in the context of a comparative discussion concerning both the original and revised structure models, along with an analysis of the trends across the series. The temperature dependence of the magnetic susceptibility of Gd(3)Ge(4) shows that it is paramagnetic at room temperature and undergoes antiferromagnetic ordering below 29 K. Magnetization, resistivity, and calorimetry data for several other members of the RE(3)Ge(4) family are presented as well.
新型二元化合物Gd₃Ge₄已被合成，并通过单晶X射线衍射确定了其结构。Gd₃Ge₄结晶于正交空间群Cmcm（编号63），晶胞参数为a = 4.0953(11) Å，b = 10.735(3) Å，c = 14.335(4) Å，Z = 4。其结构可描述为由锗原子构成的波纹层，钆原子夹在其间。Gd₃Ge₄中的键合排列也可从已知化合物GdGe（CrB型）推导而来，方法是切断GdGe中的(∞)₁[Ge₂]之字形链，并在所得三角形片段之间插入一个额外的锗原子。从形式上讲，这些特征代表了与Er₃Ge₄型（皮尔逊oC28）的同构性。然而，对整个RE₃Ge₄系列（RE = Y，Tb - Tm）晶体学的重新审视揭示了差异，并对最初确定的结构的准确性提出了质疑。这就需要对键合进行新的合理化解释，本文将在关于原始结构模型和修订结构模型的比较讨论背景下提供这种解释，并对整个系列的趋势进行分析。Gd₃Ge₄的磁化率与温度的关系表明，它在室温下是顺磁性的，在29 K以下发生反铁磁有序化。本文还给出了RE₃Ge₄家族其他几个成员的磁化、电阻和量热数据。
