First-principles calculation on phase stability and metallization in GeH4 under pressure

Li, Zhi; Yu, Wen; Jin, Changqing

doi:10.1016/j.ssc.2007.05.025

Cited by 29 publications

(26 citation statements)

References 11 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12] The motivation for examining just this group of compounds is the idea of "chemical precompression". [13] Given the difficulty of metallizing molecular H 2 [14,15] (a potential superconductor and superfluid), [13,16,17] the core concept is that the effective repulsion between hydrogen molecules might be reduced in [H,A] by the hydrogen atoms bonding to other atoms [A].…”

Section: The Question As It Emerges For Snhmentioning

confidence: 99%

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

2010

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When a molecular compound is thermodynamically unstable (but kinetically persistent) with respect to the elements, structures that contain segregated layers of the elements may be favored at moderate pressures, as a compromise between the potential stability of novel electronic configurations and decomposition into the elements (or other stable compounds). We use stannane, SnH4, to approach this quite general problem theoretically, since the heat of formation of SnH4 is so positive. Our ground‐state DFT searches for optimal structures begin with slabs formed from 1–4 layers of tin atoms in the β‐Sn and bcc configurations, and also slabs of molecular hydrogen or hydrogen atoms, preserving the overall SnH4 stoichiometry. As argued, segregated layers are an important structural feature in the lower‐ and moderate‐pressure regime (0 and 50 GPa). By 140 GPa (V/V0=0.21) the coordination of tin and hydrogen increases and the slabs disappear, as judged from the optimized structures.

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Section: The Question As It Emerges For Snhmentioning

confidence: 99%

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

2010

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“…So far, the theoretical studies have predicted high superconductivities with T C reaching 64 K at 220 GPa for GeH 4 [15] and 62 K at 200 GPa for SnH 4 [24] (for comparison: T C = 17 K for SiH 4 at 220 GPa [25]). Moreover, some estimates show that since the atomic radius and atomic masses of Ge and Sn are larger than Si, GeH 4 and SnH 4 might be easier to become a metal (at a lower metallization pressure) than silane [26].…”

Section: Introductionmentioning

confidence: 99%

Detailed study of the superconducting properties in compressed germane

Szczȩśniak

Durajski

2015

Eur. Phys. J. B

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Abstract. Hydrogen-rich compounds under extreme pressure are the most promising systems for searching a high-temperature superconductivity. In presented paper, we report analysis of the thermodynamic properties of hydrogenated germanium (germane, GeH4) at 220 GPa obtained within the framework of the Migdal-Eliashberg theory. We observe that together with the increase of Coulomb pseudopotential from 0.1 to 0.3 the critical temperature decreases from 92.36 K to 52.80 K. A similar trend is also well-visible in the case of other thermodynamic properties. Moreover, we study the influence of external pressure on the superconducting state of GeH4. On this basis we conclude that increase of pressure from 20 to 220 GPa has a pronounced effect on the thermodynamic stability of germane. Finally, it is proved that the properties of the superconducting state of GeH4 differ markedly from predictions of the Bardeen-Cooper-Schrieffer (BCS) theory.

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“…It has been proposed that hydrogen-rich compounds (e.g., group IVa hydrides (12)) are expected to metallize at pressures considerably lower than pure hydrogen due to the chemical "precompression" caused by heavier elements; these metallization pressures may fall within the range of current capabilities of static compression techniques. The exploration of potential superconductivity in these hydrogen-rich compounds (e.g., SiH 4 , GeH 4 , and SnH 4 ) is thus desirable and numerous studies have been performed (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Strikingly, recent experiments (15,18) show that SiH 4 transforms to a metallic phase near 50-60 GPa with a superconducting T c of 17 K at 96 and 120 GPa, though debate remains (26).…”

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confidence: 99%

High-pressure crystal structures and superconductivity of Stannane (SnH ₄ )

Gao

Oganov

Liu

et al. 2010

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

186

154

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There is great interest in the exploration of hydrogen-rich compounds upon strong compression where they can become superconductors. Stannane (SnH 4 ) has been proposed to be a potential high-temperature superconductor under pressure, but its high-pressure crystal structures, fundamental for the understanding of superconductivity, remain unsolved. Using an ab initio evolutionary algorithm for crystal structure prediction, we propose the existence of two unique high-pressure metallic phases having space groups Ama2 and P6 3 ∕mmc, which both contain hexagonal layers of Sn atoms and semimolecular (perhydride) H 2 units. Enthalpy calculations reveal that the Ama2 and P6 3 ∕mmc structures are stable at 96-180 GPa and above 180 GPa, respectively, while below 96 GPa SnH 4 is unstable with respect to elemental decomposition. The application of the Allen-Dynes modified McMillan equation reveals high superconducting temperatures of 15-22 K for the Ama2 phase at 120 GPa and 52-62 K for the P6 3 ∕mmc phase at 200 GPa.hydrogen-rich compounds | metallization | electron-phonon coupling R elatively high-temperature superconductivity is now documented in light-element metals such as Li under pressure (1-3) and MgB 2 (4), where transition temperatures T c up to 20 K and 39 K, respectively, are observed. There is great interest in exploration of unique superconducting phases in other lightelement materials because their high phonon frequencies can enhance electron-phonon coupling (see ref. 5). As the lightest element, hydrogen at very high densities is also predicted to be a superconductor with high transition temperatures (6-8). Experiments indicate that the predicted metallic and superconducting states of hydrogen remain above ∼300 GPa (9-11). It has been proposed that hydrogen-rich compounds (e.g., group IVa hydrides (12)) are expected to metallize at pressures considerably lower than pure hydrogen due to the chemical "precompression" caused by heavier elements; these metallization pressures may fall within the range of current capabilities of static compression techniques. The exploration of potential superconductivity in these hydrogen-rich compounds (e.g., SiH 4 , GeH 4 , and SnH 4 ) is thus desirable and numerous studies have been performed (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Strikingly, recent experiments (15,18) show that SiH 4 transforms to a metallic phase near 50-60 GPa with a superconducting T c of 17 K at 96 and 120 GPa, though debate remains (26). We have recently predicted (17) that GeH 4 becomes a high-temperature superconductor with a T c of 64 K at 220 GPa. A theoretical study of SnH 4 (21) predicts that its T c can be even higher, reaching the value of 80 K. Using simulated annealing and geometry optimization, that study found that the high-pressure phase of SnH 4 has P6∕mmm symmetry with a layered structure intercalated by molecular H 2 units, wherein the nearest H-H distance, 0.84 Å, is short enough to be considered as covalent bonding, but significantly longer than the 0.74 Å in the free H ...

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First-principles calculation on phase stability and metallization in GeH4 under pressure

Cited by 29 publications

References 11 publications

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

Detailed study of the superconducting properties in compressed germane

High-pressure crystal structures and superconductivity of Stannane (SnH ₄ )

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First-principles calculation on phase stability and metallization in GeH4 under pressure

Cited by 29 publications

References 11 publications

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH4

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH4

Detailed study of the superconducting properties in compressed germane

High-pressure crystal structures and superconductivity of Stannane (SnH 4 )

Contact Info

Product

Resources

About

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

Segregation into Layers: A General Problem for Structural Instability under Pressure, Exemplified by SnH₄

High-pressure crystal structures and superconductivity of Stannane (SnH ₄ )