| Project/Area Number |
15540460
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | Kumamoto University (2004)
Osaka University (2003) |
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Principal Investigator |
YOSHIASA Akira Kumamoto University, Faculty of Science, Professor, 理学部, 教授 (00191536)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | in situ experiments / the Earth's mantle conditions / local structure of melt / local structure of glass / local structure of gel / transformation of disordered phases / pressure dependences of coordination environments / EXAFS method / 優体の構造 |
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| Research Abstract |
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.
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