Mudring Anja-Verena, Corbett John D
Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011 USA.
J Am Chem Soc. 2004 Apr 28;126(16):5277-81. doi: 10.1021/ja030216b.
Theoretical reasons for metallic behavior among diverse Zintl phases have generally not been pursued at an advanced level. Here, the electronic structure of Ca5Ge3 (Cr5B3 type), which can be formulated (Ca+2)5(Ge2-6)Ge-4 in oxidation states, has been explored comparatively by means of semiempirical and first-principles density functional methods. The FP-APW calculations show that alkaline-earth-metal and germanium orbitals, particularly the d orbitals on the cations and the p-pi orbitals of the halogen-like dimeric Ge2-6, mix considerably to form a conduction band. This covalency perfectly explains the unusual metallic properties of the nominally electron-precise Zintl phase Ca5Ge3 and its numerous relatives. Similar calculational results are obtained for Sr5Ge3, Ba5Ge3, and Ca5Sn3. Cation d orbitals appear to be a common theme among Zintl phases that are also metallic.
各种津特耳相呈现金属行为的理论原因通常尚未得到深入探讨。本文采用半经验和第一性原理密度泛函方法，对Ca5Ge3（Cr5B3型，其氧化态可表示为(Ca+2)5(Ge2-6)Ge-4）的电子结构进行了比较研究。全势缀加平面波（FP-APW）计算表明，碱土金属和锗的轨道，特别是阳离子上的d轨道和类卤素二聚体Ge2-6的p-π轨道，大量混合形成导带。这种共价性完美地解释了名义上电子精确的津特耳相Ca5Ge3及其众多同类物的异常金属性质。对于Sr5Ge3、Ba5Ge3和Ca5Sn3也得到了类似的计算结果。阳离子d轨道似乎是呈现金属性的津特耳相中的一个共同特征。
