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X-ray diffraction analysis of solid hydrogen

固体氢的X射线衍射分析

基本信息

批准号：
11440125
负责人：
KAWAMURA Haruki
金额：
$ 6.98万
依托单位：
Himeji Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440125/
关键词：
X-ray powder diffraction High pressure DAC SR Low temperature Hydrogen Deuterium

项目摘要

The properties of compressed hydrogen are of fundamental interest in condensed matter and planetary physics. Recent optical studies up to 230 GPa have demonstrated that hydrogen has three solid phases, phase I, phase II and phase III.Structural studies of solid hydrogen by x-ray diffraction technique are severely restiricted because of the low scattering efficiency of hydrogen and the small size of sample at high pressure, and thus the structure of only phase I is crystallographically determined to be the hcp one by the single-crystal technique. Powder diffraction techniques, however, are still important because the fragmentation of single crystals is frequently caused at the structural transition accompanying a discontinuous change in volume. In this research, x-ray powder diffraction experiments at high pressures and low temperatures were carried out on the beam line BL10XU station at SPring-8. The wavelength was tuned with a Si (111) double-crystal monochromator to 0.6196 Å. An x-ray refractive lens made of molded PMMA was inserted in the x-ray path to enhance the density of the incident beam. The sample was exposed to an x-ray beam through a pinhole collimator of 26 μm diameter. Powder patterns were obtained by an angle-dispersive method with an image plate detector. Diamond anvil cell (DAC) were used for high pressure generation. X-ray powder diffraction studies on solid deuterium were carried out at 83 K and 94 GPa, at which conditions solid deuterium has been reported to transform into phase II.Three diffraction arcs from the sample were observed, which are assigned to the 100, 002 and 101 diffraction lines of the hcp lattice. Thus the center of each molecule is still on the hcp lattice in phase II.

压缩氢的性质是凝聚态物质和行星物理学的基本兴趣。最近的光学研究表明，在230 GPa以下，氢具有I、II和III三种固相。由于氢的散射效率低，高压下样品尺寸小，因此，通过单晶技术晶体学上确定只有相I的结构是hcp结构。然而，粉末衍射技术仍然是重要的，因为单晶的破碎经常是在结构转变伴随着不连续的体积变化。在本研究中，X射线粉末衍射实验在高压和低温下进行的光束线BL 10 XU站在SPring-8。用Si（111）双晶单色器调谐波长至0.6196 nm。由模制PMMA制成的X射线折射透镜插入X射线路径中以增强入射光束的密度。通过直径为26 μm的针孔准直器将样品暴露于X射线束。粉末图案通过具有图像板检测器的角色散方法获得。金刚石对顶砧单元（DAC）用于高压产生。在83 K和94 GPa下对固体氘进行了X射线粉末衍射研究，在此条件下固体氘转变为II相。观察到三个衍射弧，分别归属于hcp晶格的100、002和101衍射线。因此，每个分子的中心仍然在相II的hcp晶格上。