Accurate charge density determination in Zintl phases

Zintl-Klemm-Busmann概念是理解（极性）金属间化合物的结构和化学键合的最有力工具之一。所谓的Zintl相由正电性金属（碱金属、碱土金属或稀土金属）和电负性更强的p区金属或半金属元素e组成。G.属于三和弦、四和弦或五和弦。Zintl相中的化学键合通过正电性金属的价电子到负电性元素的正式的、完全的电荷转移来合理化。如果所提供的电子数不足以满足八隅体规则，则形成共价的、局部的、定向的2c 2 e-键和聚阴离子子结构。该项目的主要目的是通过Zintl阶段的实验电荷密度测定来评估这一概念。为了获得可比较的结果，研究将主要限于Ca-Si系统。将通过电弧熔化和高温技术合成足够质量的晶体。将研究使用化学迁移反应的可能性。电荷密度将从低温、高分辨率X射线和中子衍射数据的精确处理中导出。除了变形密度和电子密度的分析与原子在分子（AIM）形式主义，电子局域化函数（ELF）将近似从实验数据。这些调查将补充电子结构计算的化学键的量子化学评价。在Zintl阶段的实验电荷密度的测定是特别重要的，因为它已经宣布，因为第一次呼吁的文件。

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.