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Local structure changes and structural transformations of melt, glass and gel under the Earth's mantle conditions.

地幔条件下熔体、玻璃和凝胶的局部结构变化和结构转变。

基本信息

批准号：
15540460
负责人：
YOSHIASA Akira
金额：
$ 2.3万
依托单位：
Kumamoto University (2004)Osaka University (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

Using a large-volume high-pressure apparatus, phases of crystals, melts, glasses and gel in the system of some germanates, fluorides, halogenides and silicates have been compressed up to 15 GPa at 300-1500K. The local structure changes around the specific kind of atom have been investigated by an in situ XAFS(x-ray absorption fine structure) method using synchrotron radiation. The structures have also been characterized by means of diffraction and spectroscopic methods. Dynamical atomic motion for each atom in these phases has been studied by determined Debye-Waller factors. The atomic effective pair potentials, the phonon energies and Gruneisen parameters have been estimated in this study. For example, the coordination number of Ge in GeO2 glass changes from four to six between 8 and 10 GPa. In contrast to the case for the glass, the coordination environment around Ge in GeO2 gel gradually increases over a pressure range from 2 to 12 GPa. Liquid germinate consisting of tetrahedrally coordinated Ge contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa at 1300 K and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated Ge becomes stable. By analogy with this liquid germanate, it is expected that a sharp transition occurs in liquid silicate at a higher pressure. Geophysical implications derived from this study will be discussed with detailed data of our studies.

使用大容量高压装置，一些锗酸盐、氟化物、卤化物和硅酸盐体系中的晶体、熔体、玻璃和凝胶相在300-1500K下被压缩至15 GPa。通过使用同步辐射的原位XAFS（X射线吸收精细结构）方法研究了特定种类原子周围的局部结构变化。还通过衍射和光谱方法对结构进行了表征。通过确定的德拜-沃勒因子研究了这些相中每个原子的动态原子运动。本研究估计了原子有效对势、声子能量和格鲁内森参数。例如，GeO2 玻璃中 Ge 的配位数在 8 至 10 GPa 之间从 4 变为 6。与玻璃的情况相反，GeO2 凝胶中 Ge 周围的配位环境在 2 至 12 GPa 的压力范围内逐渐增加。由四面体配位的 Ge 组成的液态萌发物随着压力的增加而收缩，局部结构没有显着变化，在 1300 K 时高达 2.5 GPa，然后在 3 GPa 左右显示出突然的四倍到六倍的配位变化。配位变化在 4 GPa 以下完成，此时由八面体配位的 Ge 组成的高密度液体变得稳定。通过与该液体锗酸盐类比，预计液体硅酸盐在较高压力下会发生急剧转变。本研究得出的地球物理意义将通过我们研究的详细数据进行讨论。