Zhuravleva Marina A, Salvador James, Bilc Daniel, Mahanti Subhendra D, Ireland John, Kannewurf Carl R, Kanatzidis Mercouri G
Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA, Fax: (+1) 517-353-1793.
Chemistry. 2004 Jul 5;10(13):3197-208. doi: 10.1002/chem.200305755.
Two new intermetallic compounds, Yb(2)Ga(4)Ge(6) and Yb(3)Ga(4)Ge(6), were obtained from reactions in molten Ga. A third compound, Eu(3)Ga(4)Ge(6), was produced by direct combination of the elements. The crystal structures of these compounds were studied by single-crystal X-ray diffraction. Yb(2)Ga(4)Ge(6) crystallizes in an orthorhombic cell with a=4.1698(7), b=23.254(4), c=10.7299(18) A in the polar space group Cmc2(1). The structure of RE(3)Ga(4)Ge(6) is monoclinic, space group C2/m, with cell parameters a=23.941(6), b=4.1928(11), c=10.918(3) A, beta=91.426(4) degrees for RE=Yb, and a=24.136(2), b=4.3118(4), c=11.017(1) A, beta=91.683(2) degrees for RE=Eu. The refinement [I>2 sigma(I)] converged to the final residuals R(1)/wR(2)=0.0229/0.0589, 0.0411/0.1114, and 0.0342/0.0786 for Yb(2)Ga(4)Ge(6), Yb(3)Ga(4)Ge(6), and Eu(3)Ga(4)Ge(6), respectively. The structures of these two families of compounds can be described by a Zintl concept of bonding, in which the three-dimensional Ga(4)Ge(6) framework serves as a host and electron sink for the electropositive RE atoms. The structural relation of RE(3)Ga(4)Ge(6) to of Yb(2)Ga(4)Ge(6) lies in a monoclinic distortion of the orthorhombic cell of Yb(2)Ga(4)Ge(6) and reduction of the [Ga(4)Ge(6)] network by two electrons per formula unit. The results of theoretical calculations of the electronic structure, electrical transport data, and thermochemical and magnetic measurements are also reported.
通过在熔融镓中的反应得到了两种新的金属间化合物Yb(2)Ga(4)Ge(6)和Yb(3)Ga(4)Ge(6)。通过元素直接化合制备出了第三种化合物Eu(3)Ga(4)Ge(6)。利用单晶X射线衍射研究了这些化合物的晶体结构。Yb(2)Ga(4)Ge(6)结晶于正交晶胞中，在极性空间群Cmc2(1)里，a = 4.1698(7)，b = 23.254(4)，c = 10.7299(18) Å。RE(3)Ga(4)Ge(6)的结构为单斜晶系，空间群C2/m，对于RE = Yb，晶胞参数a = 23.941(6)，b = 4.1928(11)，c = 10.918(3) Å，β = 91.426(4)°；对于RE = Eu，a = 24.136(2)，b = 4.3118(4)，c = 11.017(1) Å，β = 91.683(2)°。精修[I > 2σ(I)]收敛至最终残差，对于Yb(2)Ga(4)Ge(6)、Yb(3)Ga(4)Ge(6)和Eu(3)Ga(4)Ge(6)，R(1)/wR(2)分别为0.0229/0.0589, 0.0411/0.1114和0.0342/0.0786。这两类化合物的结构可用Zintl键合概念来描述，其中三维的Ga(4)Ge(6)骨架作为主体和电子库容纳正电性的RE原子。RE(3)Ga(4)Ge(6)与Yb(2)Ga(4)Ge(6)的结构关系在于Yb(2)Ga(4)Ge(6)正交晶胞的单斜畸变以及每个化学式单位[Ga(4)Ge(6)]网络减少两个电子。还报道了电子结构的理论计算结果、电输运数据以及热化学和磁性测量结果。
