Crystal structure and volume effects in the hydrides of d metals

Соменков, В. А.; Глазков, В. П.; Irodova, A. V.; Shilstein, S.Sh.

doi:10.1016/0022-5088(87)90045-2

Cited by 62 publications

(24 citation statements)

References 5 publications

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“…2, Middle). This observation is consistent with the known NaCl-structured RhH (26). Further compressing to 8 GPa, we discovered the RhH 2 phase which remained in the fcc structure with another step of 21.2% unit-cell volume expansion (ΔV 2 ¼ 15.4 Å 3 ).…”

Section: Metal Hydrides | Phase Transitionsupporting

confidence: 90%

Rhodium dihydride (RhH₂) with high volumetric hydrogen density

Ding²,

Kim³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH 2 ) with high volumetric hydrogen density (163.7 g∕L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH 2 at 8 GPa. RhH 2 is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH 2 is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time. (1) started with a simple conjecture that, above 25 GPa, hydrogen molecules would dissociate in favor of a monatomic metal. Hydrogen may also metalize in the molecular form by pressureinduced band-gap closure (2). Moreover, metallic hydrogen has been predicted to be a high-Tc superconductor (3, 4). However, direct compression of hydrogen up to the maximum achievable static pressure of 320 GPa was still insufficient to reach the predicted metallization pressure (5) which has been revised to >400 GPa by modern theories (4). Compression of hydrogen-rich metallic alloys has been suggested as an alternative way to attain the metallic hydrogen state (6). One may think of hydrogen atoms as being "chemically precompressed" in hydrides with a small H atomic volume, thus requiring less additional compression to a metallic high-Tc state than that for pure hydrogen. This suggestion has motivated a great deal of high-pressure theoretical and experimental research on hydrogen-rich alloys. Selected examples on MH 4 (where M ¼ Si, Ge, Sn, or Pb) alone are shown in refs. 7-16.Hydrogen has also been considered as an abundant and environmental-friendly fuel of the future, but onboard hydrogen storage remains a critical issue that hinders the application (17, 18). The ideal hydrogen storage material ought to satisfy a number of criteria, including high volumetric H density, high gravimetric H content, near ambient pressure-temperature condition for H absorption/discharge, and cost effectiveness (17, 18). Although no material has yet met all criteria, extreme limits of these criteria have been pursued and explored individually. Materials with extremely high H atomic ratio (n) have been synthesized in XeðH 2 Þ 8 ðn ¼ 16Þ by high-pressure experiment (19), and NaH 9 ðn ¼ 9Þ by theory (20). BaReH 9 with a very high volumetric H density (134 g∕L) has been predicted by theory (21) to chemically precompress its discrete H 2 units in the structure and cause a dramatic lowering of the metallization pressure to 51 GPa. (22) often exists in the atomic form, filling the octahedral (o) or tetrahedral (t) site...

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Section: Metal Hydrides | Phase Transitionsupporting

confidence: 90%

Rhodium dihydride (RhH₂) with high volumetric hydrogen density

Ding²,

Kim³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Assuming a reference volume of (hypothetical) hcp and fcc Mo to be larger than bcc Mo by $0:4 Â 10 À3 nm 3 , based on the band-theoretical calculation on fcc and bcc Mo, 18) we obtain the H-induced volume of 1:7 Â 10 À3 and 2:3 Â 10 À3 nm 3 /H-atom, respectively, for hcp and fcc Mo. The small value for the hcp phase is consistent with the known data for H atoms occupying octahedral sites in the hcp lattice (1.66 for Mn-H, 2) for Tc-H 19) ). The phase diagram shown in Fig.…”

Section: Discussionsupporting

confidence: 78%

The Phase Diagram of Mo-H Alloys under High Hydrogen Pressures

Fukai

Mizutani

2003

Mater. Trans.

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The phase diagram of the Mo-H system was determined by in situ X-ray diffraction using synchrotron radiation up to 1200 C and the hydrogen pressure to p(H 2 ) = 5.3 GPa. Three phases were found to exist; a bcc phase () of low hydrogen concentrations at low hydrogen pressures, and two high-pressure phases, an hcp (") phase at lower temperatures and an fcc () phase at higher temperatures, both having a nearly stoichiometeric composition of x = [H]/[Mo] $ 1. A gradual lattice contraction observed in the fcc phase indicates the formation of superabundant Mo-atom vacancies (vacancy-hydrogen clusters).

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“…By total energy minimization, lattice parameter of the fcc rhodium structure is estimated to be 3.8966 Å, which is in good agreement with the experimental value, 4.010 Å reported by Somenkov et al [16]. The calculated binding energies for hydrogen in different interstitial sites are shown in see that the binding energy of hydrogen atom in octahedral site is lower than that in tetrahedral site, that is the octahedral site is the global minimum, the tetrahedral site being higher in energy by 0.5423eV, so the most stable position of hydrogen atom in fcc rhodium locates at the octahedral interstice, and the tetrahedral interstice is the second stable site.…”

Section: Resultssupporting

confidence: 89%

First-principles study of hydrogen diffusion in transition metal Rhodium

Bao

Cui

Wang

2015

J. Phys.: Conf. Ser.

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Abstract. In this study, the diffuse pattern and path of hydrogen in transition metal rhodium are investigated by the first-principles calculations. Density functional theory is used to calculate the system energies of hydrogen atom occupying different positions in rhodium crystal lattice. The results indicate that the most stable position of hydrogen atom in rhodium crystal lattice locates at the octahedral interstice, and the tetrahedral interstice is the second stable site. The activation barrier energy for the diffusion of atomic hydrogen in transition metal rhodium is quantified by determining the most favorable path, i.e., the minimum-energy pathway for diffusion, that is the indirect octahedral-tetrahedral-octahedral (O-T-O) pathway, and the activation energy is 0.8345eV. IntroductionResearch into the reaction of hydrogen with metals has attracted much attention because of potential applications as effective hydrogen storage materials [1], Ho K M et. al [2] studied the metal-hydrogen interactions in NbH by first-principles total energy calculations. And the transition metal-hydrogen systems have also attracted considerable interest for the unfilled d orbitals. Antonov V E [3] discussed the phase transformations, crystal and magnetic structures of high-pressure hydrides of d-metals, and obtained the conclusions that the high-pressure technique had been most effective in hydrogenation of the group VI-VIII transition metals, neither of which except Pd forms hydrides at low hydrogen pressures, and the hydrides formed at high pressures were shown to have close-packed metal sublattices with fcc, hcp or double hcp structures, in which hydrogen occupied octahedral interstitial positions. Then Pronsato M E et. al [4] investigated the electronic and bonding properties of iron monohydride using tight-binding method. We [5,6] had investigated the structural, electronic and magnetic properties of RhH alloy and PdHx with both cubic and tetrahedral structures based on abinitio total energy calculations.Hydrogen diffusion and migration in metals are important aspects to determine the behavior of hydrogen in metals. The diffusion of hydrogen in metals or alloys are also investigated by scientific workers. Diffusion of hydrogen in the α-phase Pd system was investigated by electrochemical methods [7], and the concentration of hydrogen in the metal was gradually increased by control of the electrode potential. The dissolution and diffusion behaviors of hydrogen in copper were investigated based on first-principles calculations in combination [8]. The adsorption and diffusion of hydrogen on ordered Ni 3 Fe(111) surface and in the bulk were studied by first-principles calculations based on density functional theory [9]. The hydrides of Rh were synthesized at the Institute of Solid State Physics, Russian Academy of Sciences for the first time [10,11], and RhH had a NaCl-type crystal structure with H atoms occupying every octahedral site in the face -centered cubic of rhodium lattice with the parameter a =4.010 Å. In this work, ...

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Crystal structure and volume effects in the hydrides of d metals

Cited by 62 publications

References 5 publications

Rhodium dihydride (RhH₂) with high volumetric hydrogen density

Rhodium dihydride (RhH₂) with high volumetric hydrogen density

The Phase Diagram of Mo-H Alloys under High Hydrogen Pressures

First-principles study of hydrogen diffusion in transition metal Rhodium

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Crystal structure and volume effects in the hydrides of d metals

Cited by 62 publications

References 5 publications

Rhodium dihydride (RhH2) with high volumetric hydrogen density

Rhodium dihydride (RhH2) with high volumetric hydrogen density

The Phase Diagram of Mo-H Alloys under High Hydrogen Pressures

First-principles study of hydrogen diffusion in transition metal Rhodium

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Product

Resources

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Rhodium dihydride (RhH₂) with high volumetric hydrogen density

Rhodium dihydride (RhH₂) with high volumetric hydrogen density