2005 Fiscal Year Final Research Report Summary
Study on crystal structures and compressibilities of solid hydrogen and transition metal hydrides at high pressures and high temperatures
| Project/Area Number |
16340132
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | University of Hyogo |
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Principal Investigator |
KAWAMURA Haruki University of Hyogo, Graduate School of Material Science, Material Science, Professor, 大学院・物質理学研究科, 教授 (00192005)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Solid hydrogen / Metal hydrides / DAC / SR / X-ray diffraction / High pressure |
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| Research Abstract |
(1)Solid hydrogen : At temperature-pressure range of 30K-395K and 6GPa-100GPa, X-ray diffraction experiments were performed. The diffraction peaks assigned by an hcp lattice were observed in that temperature-pressure range. Pressure dependences of molar volume of hydrogen at 30, 150, 300 and 395 K were obtained. At pressures above 20 GPa, the molar volume is scarcely dependent on temperature. Lattice constants and the c/a ratio of an hcp lattice were continuously decreased by increase in pressure across the I-II phase boundary.
(2)Metal hydrides : Rhenium metal incorporated hydrogen in interstices of its hcp lattice and formed a metal hydride at pressures above 7GPa. Hydrogen is incorporated in every second layer along the c-axis of an hcp lattice, which results in an anti-CdI_2 structure. Tungsten metal also incorporated hydrogen at pressures above 25GPa. In the rhenium hydride the arrangements of a metal sublattice did not change, while the tungsten sublattice changed from a bcc to an
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hcp when hydrogen was incorporated in a tungsten metal. The incorporated hydrogen atom randomly occupied the octahedral hole of the hcp lattice. The compressibility and the reaction with hydrogen of Fe-10%Ni alloy, which is considered to be the principal constituent of the earth's core, were investigated. The alloy incorporated hydrogen at pressure above 6 GPa and transformed from a bcc to a dhcp structure. On the other hand, the pristine alloy transformed from a bcc to an hcp at 15GPa. These transformations are similar to those of pure Fe. The transition pressures, however, are higher in the case of the alloy.
(3)Multimegabar and a pressure scale : The first-order Raman spectra of diamond anvils used in a gasketed high-pressure cell were measured at pressures up to 300GPa. The high-frequency edge of the Raman band is represented by a function of pressure in the sample chamber. The application of the pressure dependence for pressure determination up to multimegabars pressure region is proposed. Less
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Research Products
(14 results)
