High-Pressure Compounds in Methane-Hydrogen Mixtures

Somayazulu, Maddury; Finger, L. W.; Hemley, Russell J.; Mao, Ho‐kwang

doi:10.1126/science.271.5254.1400

Cited by 148 publications

(118 citation statements)

References 12 publications

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“…The highest hydrogen content in a compound is that of the van der Waals compound (H2)4CH4 discovered at HP [676,677] with 92.3% (atomic) and 50% (weight) hydrogen. Two hydrogen hydrates H2(H2O) and H2(H2O)6 were first discovered at 2 GPa [678].…”

Section: Energy Materialsmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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Pressure profoundly alters all states of matter. The symbiotic development of ultrahighpressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

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Section: Energy Materialsmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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“…The structure of Kr(H 2 ) 4 and its evolution under pressure. The structure of the Kr-H 2 compound was solved from a single-crystal data set collected at 11.24 GPa (Tab.…”

Section: Resultsmentioning

confidence: 99%

“…High-pressure Raman spectra and the H 2 sublattice of Kr(H 2 ) 4 . The Raman spectra of Kr(H 2 ) 4 are characterised by roton peaks between 200-1200 cm 21 and by a maximum of four H 2 vibrons between 4200-4500 cm 21 confirming the presence of molecular hydrogen in the structure (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…At gigapascal pressures the atomic rare gases (e.g., He, Ar, Xe), diatomic molecules (e.g., H 2 , N 2 , O 2 ) and even full-shell molecules (e.g., CH 4 , SiH 4 ) can interact with each other and form compounds. The first reported, pressure-stabilized, stoichiometric van der Waals (vdW) solid was reported in the He-N 2 system, He(N 2 ) 11 1 .…”

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confidence: 99%

“…The first reported, pressure-stabilized, stoichiometric van der Waals (vdW) solid was reported in the He-N 2 system, He(N 2 ) 11 1 . Since then a variety of stoichiometric vdW compounds have been synthesised under pressure for example, in the systems He-Ne 2 , Ar-H 2 3 , CH 4 -H 2 4 , and most recently Xe-H 2 5,6 . The study of hydrogen-rich binary mixtures has attracted particular attention because they are of interest to planetary science and astronomy, are potentially relevant technologically for hydrogen storage 7 , and, last but not least, offer the tantalising prospect to promote the pressure-induced insulator-metal transition in hydrogen at a lower pressure than required for pure hydrogen (e.g., 3,8).…”

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confidence: 99%

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New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system

Kleppe

Amboage

Jephcoat

2014

Sci Rep

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The application of pressure to materials can reveal unexpected chemistry. Under compression, noble gases form stoichiometric van der Waals (vdW) compounds with closed-shell molecules such as hydrogen, leading to a variety of unusual structures. We have synthesised Kr(H2)4 for the first time in a diamond-anvil high-pressure cell at pressures ≥5.3 GPa and characterised its structural and vibrational properties to above 50 GPa. The structure of Kr(H2)4, as solved by single-crystal synchrotron X-ray diffraction, is face-centred cubic (fcc) with krypton atoms forming isolated octahedra at fcc sites. Rotationally disordered H2 molecules occupy four different, interstitial sites, consistent with the observation of four Raman active H2 vibrons. The discovery of Kr(H2)4 expands the range of pressure-stabilised, hydrogen-rich vdW solids, and, in comparison with the two known rare-gas-H2 compounds, Xe(H2)8 and Ar(H2)2, reveals an increasing change in hydrogen molecular packing with increasing rare gas atomic number.

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