Electron Density Distribution of Hydrogen in Solids Obtained by the Maximum Entropy Method

本科学研究旨在实验研究固体中氢的精确电子密度分布。为此，作为研究的一部分，开发了一种称为最大熵法（MEM）的新方法。为了建立该方法，将MEM应用于粉末x射线衍射数据，得到了各种材料的电子密度分布。发现MEM是一种非常有效的方法，可以将精确测量的x射线衍射数据以电子密度的形式可视化。对于固体中氢的电子密度，发现氢键情况下的电子密度分布更像共价键电子，而非氢键情况下的电子密度分布非常球形。发现球形分布的离子电荷对应于氢的负离子。在这两种情况下，假设氢作为自由原子在固体中的电子分布是不合适的。似乎没有理由在最小二乘细化中使用氢的原子形状因子。这增加了用x射线衍射在固体中寻找氢的难度。今后将利用最大熵法在许多材料中观测氢的精确电子密度分布。

This scientific research aimed to investigate experimentally the pre- cise electron density distribution of hydrogen in solies. For that purpose, a new method called the Maximum Entropy Method (MEM) was developed as a part of the research. In order to establish the method, electron density distributions of various materials were obtained by applying MEM to powder X-ray diffraction data. It was found that MEM was very powerful method to visualize the accurately measured X-ray diffraction data in the form of electron densities. As for electron densities of hydrogen in solids, it was revealed that electron densities in the case of hydrogen bond distributed more like covalent bond electrons, whereas very spherical density distribu- tion of electrons were observed in the case of non-hydrogen bonding. The ionic charge of spherical distribution was found to correspond to negative ion of hydrogen. In both cases, it not appropriate to assume the distribu- tion of electrons of hydrogen in solids as a free atom. It seems that there is no justification to use the atomic form factor of hydrogen in the least squares refinement. This increases the difficulties to find the hydrogen in solids by X-ray diffraction. The precise electron density distribution of hydrogen will be observed by the Maximum Entropy Method in many materials in future.