Determination of the crystal distortion caused by stereochemically active lone electron pairs.

测定由立体化学活性孤电子对引起的晶体畸变。

• 批准号: 466418279
• 负责人: Professor Dr. Thorsten Michael Gesing
• 金额: --
• 依托单位: Institut für Anorganische Chemie und Kristallographie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/466418279?language=en
• 关键词: Determination; crystal; distortion; caused; stereochemically

Structural distortion away from ideal polyhedra and polyhedral arrangements can have multiple causes and always influences the crystal-chemical and crystal-physical properties of a solid. For the understanding of structure-property relationships, which are crucial for the development of any application, the origin of these distortions and their precise measurement is of pivotal importance.One such factors is a stereochemical active lone pair (LEP), whose strength can be theoretically described by the Liebau density vector. Experimentally however, up to now, we can only access the atomic distortion of a polyhedral coordination using the Wang-Liebau eccentricity (WLE) parameter. This measurement is intrinsically flawed in determining the influence of the LEP, because it does not allow to separate out this influence from all other possible influences on distortion (for example Jahn-Teller-distortion, Quadratic elongation, or Halasyamani distortion). However, nature may offer a perfect tool of exploration of this question because the lanthanide contraction results in the fact that elements of the 5th and 6th period have almost the same size, and hence should – geometrically at least – lead to isostructural materials. However, elements of period 5 display large LEPs, whereas those of period 6 are smaller due to the relativistic effect attraction. Thus, if one chooses a pair of materials, in which one contains a period 5 element and the other a period 6 element at the same position, one can make a direct assessment of the contribution of the LEP to the WLE. This would give only two distinct values, but if one views this pair of materials as the extremes of a solid solution in which these two elements can be mixed in any ratio, one may obtain a finely resolved tool for this assessment, which is of fundamental value for solid state chemistry and crystallography.We believe that mullite-type compound pairs of the composition PbMBO4 / SnMBO4 (M = Al, Ga, Cr, Mn, and Fe) and the solid solutions that connect them will provide the ideal platform to study and separate the influence of the lone pair.We therefore propose to synthesize these materials (some of which have been described by us and others), and to assess their crystal structures in terms of their physical properties (thermal expansion, thermal phase stability, bandgap behavior or magnetic properties) This will give the material and temperature dependent WLE in hand with the influence on the physical properties. In addition, DFT methods will be used to calculate the LDV, providing information on the electron density of the LEP and its direction. Having accumulated these data, we will synergize these findings and be able to generate a new conceptional model of the real influence of the LEP on distortion.

结构扭曲的Hedra和多面体排列可以具有多种原因，并且始终影响固体的晶体晶体化学晶体 - 物理特性，以理解结构最佳关系的阳离子，这些扭曲的起源是Pivortal重要性的。这些因素是一个静态的孤独对（LEP），是Liebau密度载体LEP，因为它不会分离对扭曲的其他可能的影响 - teller -teller -distotion，二次伸长或halasyamani Distotion的影响，但自然可能会提供理想的探索工具第五和第六阶段的元素几乎具有相同的大小，因此，至少几何形状会导致等值材料。如果一个人选择一对材料，其中一种材料包含一个周期5，另一个材料在同一时期6个元素将直接评估对WLE的贡献。材料作为固体溶液的极端，在其中tholements可以为固态化学和晶体学评估。我们相信组成PBMBO4 / SNMBO4的化合物化合物对类型因此，我们建议将这些材料（其中一些由我们和其他人描述），带镜头行为或磁性属性合成这些材料（其中一些重量），这将指导材料和温度依赖的WLE，并影响对材料和温度依赖的WLE，并具有对影响的影响thysical特性。此外，DFT方法将计算出LDV，即累积这些数据的电子密度。