Linking Intermetallics and Zintl Phases: Experimental and Theoretical Studies of Ternary "Trielides"

连接金属间化合物和 Zintl 相：三元“Trielides”的实验和理论研究

• 批准号: 9627161
• 负责人: Gordon Miller
• 金额: $ 30万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-12-01 至 2000-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9627161&HistoricalAwards=false
• 关键词: Linking; Intermetallics; Zintl; Phases; Experimental

Abstract DMR-9627161 Miller The role of valence electron concentration (vec = electron/atom ratio) to influence structure is well documented for Zintl phases (valence compounds of electropositive metals with post-transition elements: covalent networks and cages involving two-center two-electron bonds) and Hume-Rothery phases (intermetallic compounds of late and post-transition elements: dense packings involving "metallic" bonds). Zintl phases occur for vec 4 (based upon the network of post-transition elements) and Hume-Rothery phases are observed for vec ~ 2. To date, there is no systematic investigation of the broad region in vec between these two extremes. Since the two established compound classes show dramatic differences in structural principles and electronic properties, studies involving compounds with vec in the intermediate regime will provide a means of examining the transformation from one class to the other. This research involves the synthesis and detailed characterization of ternary compounds in- volving (i) an electropositive alkaline earth or rare earth metal; (ii) either a late transition metal, i.e. groups 8-12 elements or one of either Li or Mg; and (iii) a group 13 element (Al, Ga, In), called "trielides," in order to probe materials with vec between two and four by tuning the electron count. Synthetic strategies will include high temperature methods (arc-melting) and using metallic fluxes. Products will be examined for their crystal structure, composition, and physical properties. In particular, X-ray and neutron diffraction, electron microscopy, thermal analysis, X-ray photoelectron spectroscopy, electrical resistivity, and magnetic susceptibility measurements will be utilized. Later stages of this investigation will involve the incorporation of boron, carbon, and nitrogen into these intermetallics. In addition to these experimental approaches, theoretical methods will be applied to investigate the valence electron distribution in thes e systems as the vec changes. Specifically, relationships between these solids and molecular analogues, e.g., ranging from metallocarborane deltahedra to Zintl-type anionic cages, will be explored. Semiempirical electronic structure calculations will be used to examine the ternary systems under study, with the aspirations of adapting the LMTO calculations to these complex systems. %%% This investigation represents the first concerted effort of experiment and theory to perform a systematic examination of compounds linking complex intermetallics with complex valence compounds. The ternary compounds in this investigation may show high electrical conductivities coupled with regions of strong covalent bonding. Therefore, these materials may offer potential applications as high temperature metals, or may provide a means of studying either strengthening or embrittlement mechanisms in intermetallics.

摘要DMR-9627161 Miller在ZINTL阶段（带有后过渡后元件的电阳性金属的价化合物）对价值电子浓度（VEC =电子/原子比）对影响结构的作用有充分的文献记载：涉及两中性两中性键合的网络和笼子和蜂巢的近期和蜂巢的phases和Hume hume的phases and hume phases（元素：涉及“金属”键的密集包装）。 VEC 4（基于过渡后元素网络）发生了ZINTL阶段，并且在VEC〜2中观察到了休ume的相位。由于两个已建立的化合物类别显示在结构原理和电子特性方面存在巨大差异，因此涉及中级状态中具有VEC化合物的研究将提供一种检查从一个类向另一个类别转变的方法。 这项研究涉及三元化合物含量的合成和详细表征（i）电阳性碱土或稀土金属； （ii）要么是晚期过渡金属，即8-12组或LI或MG之一； （iii）一个13组元素（Al，Ga，in）称为“ trielides”，以通过调整电子计数在两到四个之间的VEC探测材料。合成策略将包括高温方法（ARC熔化）和使用金属通量。将检查产品的晶体结构，组成和物理特性。特别是，将利用X射线和中子衍射，电子显微镜，热分析，X射线光电子光谱，电阻率和磁敏感性测量值。这项研究的后期阶段将涉及将硼，碳和氮掺入这些金属间。除了这些实验方法外，随着VEC的变化，理论方法还将应用理论方法研究该系统中的价电子分布。具体而言，将探索这些固体与分子类似物之间的关系，例如，将探索从金属果硼烷deltahedra到Zintl型阴离子笼的关系。半经验电子结构计算将用于检查正在研究的三元系统，并渴望将LMTO计算适应这些复杂系统。 %% %%这项研究代表了实验和理论的第一个协同工作，以对将复杂的金属合理与复杂价化合物联系起来进行系统检查。这项研究中的三元化合物可能显示出高电导率以及较强的共价键区域。因此，这些材料可以作为高温金属提供潜在的应用，或者可以提供一种研究金属间增强或封闭机制的方法。