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

本研究的目的有三个。它们是：1)建立新开发的复杂材料的精确结构分析方法，如富勒烯化合物；2)找出准确的结构。这些材料的结构，特别是电子水平上的面内金属富勒烯化合物，以及3)提出了具有强大计算能力的现代结晶学的下一步。首先，我们发现Rietveld精化和最大熵方法(Rietveld/MEM)的结合是一种非常有效的方法来精炼任何粉末形式的晶体化合物的电荷密度分布。这对于找出富勒烯化合物的准确结构是非常有用的，因为面内金属富勒烯化合物只能以粉末的形式获得。这使得富勒烯化合物中有时出现的结构变化具有灵活性，例如单个原子的半球分布。利用RietveldMEM，不仅得到了像M@C_&lt；82&gt；这样的面内金属富勒烯的精确的电子密度分布，而且还得到了微孔金属有机固体，如CPL-1(具有柱层结构的配位聚合物1)的电子密度分布。在后一种情况下，实验获得的MEM电子密度表明，物理吸附的氧分子的van der Waals二聚体位于纳米通道的中间，并形成与宿主通道结构平行的一维梯形结构。在这两种情况下，同步加速器粉末X射线数据都用于RietveldMEM分析。考虑到这些事实，第二个目标完成了。为了研究第三个目标，本项目提前一年结束，新项目在这个项目之后开始。

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.