Development of new system for accurate charge density analysis of advanced materials

点击翻译按钮获取中文摘要

There are three aims of this study. They are 1) to establish the accurate structure analytical method for newly developed sophisticated materials, such as fullerene compounds, 2) to find out the accurate. structure of these materials, particularly, endohedral metallo-fullerene compounds at electron level and 3) to propose next step of modern crystallography in which huge computing power is available. First of all, it was find out that the combination of Rietveld refinements and the Maximum Entropy Method (Rietveld/MEM) was a very powerful method to refine accurate charge density distributions of any crystalline compounds in powder form. This is extremely useful to find out accurate structure of fullerene compounds, because endohedral metallo-fullerene compounds can be obtained only in powder form. This allows flexibility of structural varieties sometimes occurred in fullerene compounds ; such as hemispherical distribution of a single atom. There is no doubt first aim is completedBy using RietveldMEM, accurate electron density distributions were obtained not only for endohedral metallo-fullerene such as M@C_<82>, where M represents Lantanide metals, but also micro porous metal-organic solids, such as CPL- 1 (coordination polymer 1 with pillared layer structure). In the latter case, the experimentally obtained MEM electron density revealed that van der Waals dimmers of physisorbed oxygen molecules locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. In both cases, synchrotron powder X-ray data are used for RietveldMEM analysis. Considering these facts, the second aim is completed.In order to study the third aim, the present project terminated one year earlier and the new project has been started following this project.