Dai Jing-Cao, Corbett John D
Ames Laboratory, DOE and Department of Chemistry, Iowa State University, Ames, Iowa 50010, USA.
Inorg Chem. 2007 May 28;46(11):4592-8. doi: 10.1021/ic070142v. Epub 2007 Apr 17.
The title compounds were prepared from the elements by high-temperature solid-state synthesis techniques. X-ray structural analyses shows that BaAu2In2 (1) and SrAu2In2 (2) crystallize in a new orthorhombic structure, Pnma, Z=4 (a=8.755(2), 8.530(2) A; b=4.712(1), 4.598(1) A; c=12.368(3), 12.283(4) A, respectively). Gold substitutes for 50% of the indium atoms in the tetragonal BaIn4 and monoclinic SrIn4 parents to give this new and more flexible orthorhombic structure. The Ae atoms in this structure are contained within chains of hexagonal prisms built of alternating In and Au that have additional augmenting atoms around their waists from further condensation of parallel displaced chains. The driving forces for these structural changes are in part the shorter Au-In distances (2.72 and 2.69 A) relative to d(In-In) in the parents, presumably because of relativistic contractions with Au. Generalities about such centered prismatic building blocks and their condensation modes in these and related phases are described. Band structure calculations (EHTB) demonstrate that the two compounds are metallic, which is confirmed by measurements of the resistivity of 1 and the magnetic susceptibilities of both.
通过高温固态合成技术由元素制备出了标题化合物。X射线结构分析表明，BaAu₂In₂（1）和SrAu₂In₂（2）以新的正交结构Pnma结晶，Z = 4（a分别为8.755(2)、8.530(2) Å；b分别为4.712(1)、4.598(1) Å；c分别为12.368(3)、12.283(4) Å）。在四方晶系的BaIn₄和单斜晶系的SrIn₄母体中，金替代了50%的铟原子，从而形成了这种新的且更灵活的正交结构。该结构中的Ae原子包含在由交替的铟和金构成的六棱柱链中，这些六棱柱在其腰部周围还有来自平行位移链进一步缩合的额外增强原子。这些结构变化的驱动力部分是相对于母体中d(In-In)而言较短的Au-In距离（2.72和2.69 Å），这可能是由于金的相对论收缩效应。描述了这些及相关相态中此类中心棱柱结构单元及其缩合模式的一般性情况。能带结构计算（EHTB）表明这两种化合物是金属性的，这通过对1的电阻率以及两者的磁化率的测量得到了证实。
