No evidence of metallic methane at high pressure

Martínez-Canales, Miguel; Bergara, Aitor

doi:10.1080/08957950601104955

Cited by 21 publications

(11 citation statements)

References 27 publications

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“…All of them show up interesting new structures and novel properties under pressure. CH 4 is still an insulator up to the pressure of 520 GPa4. Although Eremets et al experimentally reported the metallization and superconductivity of SiH 4 above 60 GPa5, for the controversial result it might be understood as superconductivity of amorphous silicon, silicon hydrides, or platinum hydrides67.…”

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Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

Cheng

Zhang

Wang

et al. 2015

Sci Rep

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High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc.

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Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

Cheng

Zhang

Wang

et al. 2015

Sci Rep

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“…4,5 Hydrogen can be viewed in these systems as being "chemically precompressed," which lowers the metallization pressure. While the conditions for forming metallic methane have not been reached experimentally, 6 recent theoretical studies predict that both SiH 4 ͑Refs. 5 and 7͒ and GeH 4 ͑Ref.…”

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confidence: 99%

Crystal structure ofSiH4at high pressure

et al. 2007

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The crystal structure of a high-pressure phase of silane ͑SiH 4 ͒, observed between 10 and 25 GPa, is solved using powder synchrotron x-ray diffraction and shown to be of the SnBr 4 type. The phase is an insulating molecular solid with a monoclinic unit cell containing four tetrahedrally bonded molecules, space group P2 1 / c. Ab initio calculations show the SnBr 4 -type structure to be favored in this pressure range relative to other recently proposed structures. The fit of the pressure dependence of volume to the Birch-Murnagham equation of state gives the following parameters at ambient pressure if K 0 Ј is fixed to 4: V 0 = 250͑9͒ Å 3 and K 0 = 7.8͑9͒ GPa for the experimental data, and V 0 = 255͑2͒ Å 3 and K 0 = 6.1͑2͒ GPa for the data obtained from ab initio calculations.

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“…By way of example we present in Figure 4 the electronic density of states (DOS) calculated for Phases VII and VIII at 300 GPa (the corresponding band structures are in the SM). We emphasize that the overall DOS is very much free-electron like in a three dimensional context; in the DOS there is no sign of the gap (as in the case of CH 4 ) or pseudo-gap found in calculations on other EH 4 systems (E = Si, Ge, Sn) [14,21,22,23,24,25,26].…”

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