Accurate charge density determination in Zintl phases

准确测定 Zintl 相中的电荷密度

• 批准号: 132218172
• 负责人: Professor Dr. Thomas F. Fässler
• 金额: --
• 依托单位: Lehrstuhl für Anorganische Chemie mit Schwerpunkt Neue Materialien
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2009
• 资助国家: 德国
• 起止时间: 2008-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/132218172?language=en
• 关键词: Accurate; charge; density; determination; Zintl

One of the most powerful tools for the understanding of structures and chemical bonding in (polar) intermetallic compounds is the Zintl-Klemm-Busmann concept. So-called Zintl phases consist of an electropositive metal (alkali, alkaline earth, or rare earth) and a more electronegative p-block metallic or semimetallic element e. g. of the group of the triels, tetrels or pentels. The chemical bonding in Zintl phases is rationalized by a formal, complete charge transfer of the valence electrons of the electropositive metal to the electronegative element. If the number of donated electrons is not sufficient to fulfil the octet rule, covalent, localized, directional 2c2e-bonds and polyanionic substructures are formed. The main purpose of this project is the evaluation of this concept by experimental charge density determinations in Zintl phases. In order to obtain comparable results, the investigations will mainly be restricted to the system Ca-Si. Crystals of sufficient quality will be synthesized by arc melting and high-temperature techniques. The possibility of using chemical transport reactions will be investigated. The charge densities will be derived from an accurate treatment of low temperature, high- resolution X-ray and neutron diffraction data. Apart from the analysis of the deformation density and of the electron density with the Atoms-In-Molecules (AIM) formalism, the Electron Localization Function (ELF) will be approximated from the experimental data. These investigations will be supplemented by electronic structure calculations for a quantum chemical evaluation of the chemical bonding. The determination of the experimental charge density in Zintl phases is of particular importance, as it has been announced since the first call for papers.

Zintl-Klemm-Busmann概念是理解（极性）金属间化合物结构和化学键的最有力工具之一。所谓的Zintl相由正电性金属（碱、碱土或稀土）和电负性更强的p块金属或半金属元素（如三、四、五）组成。Zintl相中的化学键是由正电金属的价电子向电负性元素的正式、完整的电荷转移来合理化的。如果供体电子的数量不足以满足八隅体规则，则形成共价的、局域的、定向的2c2e键和聚阴离子亚结构。这个项目的主要目的是通过在Zintl相中测定实验电荷密度来评估这一概念。为了获得可比较的结果，研究将主要局限于Ca-Si体系。高质量的晶体将通过电弧熔炼和高温技术合成。将研究利用化学传递反应的可能性。电荷密度将通过对低温、高分辨率x射线和中子衍射数据的精确处理得到。除了用原子-分子（AIM）的形式分析变形密度和电子密度外，还将根据实验数据近似计算电子局域函数（ELF）。这些研究将被用于化学键的量子化学评价的电子结构计算所补充。在Zintl相中实验电荷密度的测定是特别重要的，因为它在第一次论文征集时就已经宣布了。