Metal Hydrides under High Hydrostatic Pressure

Filipek, S.M.

doi:10.2978/jsas.19.1

Cited by 11 publications

(6 citation statements)

References 57 publications

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“…This corresponds to a Ir-H distance of 2.021 Å at zero pressure. A similar change in mechanical properties is only known for chemically produced hexagonal copper hydride where the bulk modulus drops from 142 to 70 GPa, a phenomenon attributed to the hydrogen-metal bond which is partly covalent and ionic [24,25]. However, copper hydride still exhibits a closedpacked structure.…”

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confidence: 90%

High-Pressure Synthesis and Characterization of Iridium Trihydride

Scheler

Marqués

Konôpková³

et al. 2013

Phys. Rev. Lett.

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We have performed in situ synchrotron x-ray diffraction studies of the iridium-hydrogen system up to 125 GPa. At 55 GPa, a phase transition in the metal lattice from the fcc to a distorted simple cubic phase is observed. The new phase is characterized by a drastically increased volume per metal atom, indicating the formation of a metal hydride, and substantially decreased bulk modulus of 190 GPa (383 GPa for pure Ir). Ab initio calculations show that the hydrogen atoms occupy the face-centered positions in the metal matrix, making this the first known noninterstitial noble metal hydride and, with a stoichiometry of IrH 3 , the one with the highest volumetric hydrogen content. Computations also reveal that several energetically competing phases exist, which can all be seen as having distorted simple cubic lattices. Slow kinetics during decomposition at pressures as low as 6 GPa suggest that this material is metastable at ambient pressure and low temperatures.

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High-Pressure Synthesis and Characterization of Iridium Trihydride

Scheler

Marqués

Konôpková³

et al. 2013

Phys. Rev. Lett.

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“…13 This can be attributed to the hydrogen-copper bond which has been described as partly covalent and ionic. 14,15 Chemically produced CuH is unstable at ambient conditions, but at temperatures a) E-mail: e.gregoryanz@ed.ac.uk below −5 • C, it can be stored permanently. 16 At room temperature it decomposes at pressures below 8.4(6) GPa.…”

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High-pressure synthesis of noble metal hydrides

Donnerer

Scheler

Gregoryanz

2013

The Journal of Chemical Physics

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The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures.

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“…The phase has an hcp structure with ideal composition RH 3 (R ¼ Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, or Lu) [1]. It is known to transform to an fcc structure at high pressures [2][3][4][5].…”

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“…This is clear evidence for the hydrogen-induced valence transition of EuH x . for EuH x -I, B 0 ¼ 11:2ð2Þ GPa and V 0 ¼ 39:8ð1Þ # A 3 for EuH x -II, B 0 ¼ 14:33ð7Þ GPa and V 0 ¼ 32:82ð3Þ # A 3 for EuH x -IV. The volume data of pure bcc-Eu were taken from Ref.…”

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Structural and Valence Changes of Europium Hydride Induced by Application of High-PressureH2

et al. 2011

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Europium hydride EuH(x), when exposed to high-pressure H₂, has been found to exhibit the following structural and valence changes: Pnma(x = 2, divalent) → P6₃/mmc(x = 2, 7.2-8.7 GPa) → I4/m(x > 2, 8.7-9.7 GPa) → I4/mmm(x > 2, 9.7 GPa-,trivalent). With a trivalent character and a distorted cubic fcc structure, the I4/mmm structure is the β phase commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH(x) is no longer an irregular member of the rare-earth metal hydrides.

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Metal Hydrides under High Hydrostatic Pressure

Cited by 11 publications

References 57 publications

High-Pressure Synthesis and Characterization of Iridium Trihydride

High-Pressure Synthesis and Characterization of Iridium Trihydride

High-pressure synthesis of noble metal hydrides

Structural and Valence Changes of Europium Hydride Induced by Application of High-PressureH2

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