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Neutron diffraction study of structure of molten alkali hydroxides

熔融碱金属氢氧化物结构的中子衍射研究

基本信息

批准号：
63470008
负责人：
OKADA Isao
金额：
$ 2.88万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

1. Neutron scattering measurements have been performed for molten LiOD, NAOD, and KOD using a nickel metal cell. Large scattering intensities by the cell could be successfully subtracted from the observed total intensities. The structure factors and their Fourier transformations reveal that the polyatomic ion can possess an effective ionic radius.2. Fine structure of molten LiOH has been elucidated from molecular dynamics simulation combined with the neutron scattering measurement.(1) Li^+ ion coordinates OH^- ion mainly on the 0 atom side. The most probable location is that r_<LiO> = 1.95 A^^ﾟ and rheta_<Li-O-H> = 115ﾟ, which is somewhat different from that of LiOH molecule in vacuum.(2) The Li^+ ion coordinates in a certain probability also on the H atom side. This is one of the characteristics of liquids which cannot be found in the solid.(3) With regard to the framework structure of the melt, OH^- ion takes tetrahedral coordination around Li^+ ion. On the other hand, four Li^+ ions coordinate just to the O atom of the OH^- ion to form a slightly folded square plane.3. Polarized and depolarized Raman scattering measurements have also been accomplished for LiOH, NaOH, KOH, RbOH, and CsOH. Band contour analysis revealed that vibrational relaxation rate depends largely on the counter cations, while rotational relaxation rate does not so much. Also in the rotational autocor relation function, oscillatory rapid decay at small t and exponential slow one at large t are found. The former is caused by the liberation of the OH^- ion and the latter seems to be accompanied by structural rearrangement of the surrounding Li^+ ions.

1. 使用镍金属电池对熔融 LiOD、NAOD 和 KOD 进行中子散射测量。细胞的大散射强度可以成功地从观察到的总强度中减去。结构因素及其傅里叶变换揭示了多原子离子可以具有有效的离子半径。 2．通过分子动力学模拟结合中子散射测量，阐明了熔融LiOH的精细结构。(1)Li^+离子主要在0原子侧配位OH^-离子。最可能的位置是r_<LiO>=1.95A^^ﾟ和rheta_<Li-O-H>=115ﾟ，这与真空中LiOH分子的位置有些不同。(2)Li^+离子也以一定概率配位在H原子一侧。这是液体所没有的固体特性之一。(3)从熔体的骨架结构来看，OH^-离子在Li^+离子周围呈四面体配位。另一方面，四个Li^+离子恰好与OH^-离子的O原子配位，形成稍微折叠的正方形平面。3．还完成了 LiOH、NaOH、KOH、RbOH 和 CsOH 的偏振和去偏振拉曼散射测量。能带轮廓分析表明，振动弛豫率很大程度上取决于抗衡阳离子，而旋转弛豫率则不太重要。同样在旋转自相关函数中，发现小 t 时振荡快速衰减，大 t 时指数缓慢衰减。前者是由 OH^- 离子的释放引起的，后者似乎伴随着周围 Li^+ 离子的结构重排。