Synthesis of molecular metallic barium superhydride: pseudocubic BaH12

Chen, Wuhao; Semenok, Dmitrii V.; Kvashnin, Alexander G.; Huang, Xiaoli; Kruglov, Ivan A.; Galasso, Michele; Song, Hao; Duan, Defang; Goncharov, Alexander F.; Prakapenka, Vitali B.; Oganov, Artem R.; Cui, Tian

doi:10.1038/s41467-020-20103-5

Cited by 96 publications

(83 citation statements)

References 59 publications

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“…[75] Moreover, the only polyhydrides of barium that have been made under high pressure are Ba 8 H 46 [76] and BaH 12 . [77] Trivalent metals…”

Section: Divalent Metalsmentioning

confidence: 99%

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Zurek

2021

Chemistry A European J

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Tetrahydrides crystallizing in the ThCr 2 Si 2 structure type have been predicted to become stable for a plethora of metals under pressure, and some have recently been synthesized. Through detailed first-principles investigations we show that the metal atoms within these I4=mmm symmetry MH 4 compounds may be divalent, trivalent or tetravalent. The valence of the metal atom and its radius govern the bonding and electronic structure of these phases, and their evolution under pressure. The factors important for enhancing superconductivity include a large number of hydrogenic states at the Fermi level, and the presence of quasi-molecular H dÀ 2 units whose bonds have been stretchedand weakened (but not broken) via electron transfer from the electropositive metal, and via a Kubas-like interaction with the metal. Analysis of the microscopic mechanism of superconductivity in MgH 4 , ScH 4 and ZrH 4 reveals that phonon modes involving a coupled libration and stretch of the H dÀ 2 units leading to the formation of more complex hydrogenic motifs are important contributors towards the electron phonon coupling mechanism. In the divalent hydride MgH 4 , modes associated with motions of the hydridic hydrogen atoms are also key contributors, and soften substantially at lower pressures.

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“…[75] Moreover, the only polyhydrides of barium that have been made under high pressure are Ba 8 H 46 [76] and BaH 12 . [77] Trivalent metals…”

Section: Divalent Metalsmentioning

confidence: 99%

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Zurek

2021

Chemistry A European J

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“…Among the predicted cubic structures that matches the X-ray diffraction pattern, the 𝐹𝑚3 $ 𝑚 BaH12 consists of highly symmetric H cubooctahedra that occupy the E O sites of FCC Ba. However, the energy of this structure is significantly higher than the distorted cubic structures such as the P21 and the Cmc21 structures 28 (Fig. 5d).…”

Section: Resultsmentioning

confidence: 89%

“…However, BaH12 in this structure is significantly higher in energy than a distorted structure with P21 symmetry, although the Ba lattice in the latter structure forms a slightly distorted FCC lattice. 28 The stability trend of these structures is hard to be explained by the direct chemical interactions between metals and H.…”

mentioning

confidence: 99%

Chemical templates that assemble the metal superhydrides

Sun

Miao

2021

Preprint

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The recent incessant discoveries of high-pressure hydrides totally altered our road map toward finding room temperature superconductors. Especially, metal superhydrides consisting of hydrogen covalent networks that resemble metallic hydrogen are favorable candidates for improving Tc and lowering pressure. However, the chemical force that drives the dissociation of H2 and the formation of H covalent network in superhydrides is unknown. Our high-throughput calculations show that, after removing H atoms, the remaining metal lattices exhibit unusual electron occupations at the interstitial regions, which matches excellently to the H lattice like a template. Furthermore, H lattices consist of 3D aromatic building units that are greatly stabilized by chemical templates of metals close to s-d boarder. The theory can help predicting ternary superhydrides that may form at lower pressure.

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“…Recently rare earth Lanthanum (or Yttrium) hydrides are also experimentally reported to be superconductive with Tc exceeds 200 K [12][13][14][15][16] . However, there are no experimental observations for superconductivity above 200 K so far in alkaline earth superhydrides, in spite of the superconductivity with Tc ~20 K was reported in barium hydrides [17] . Here, we report the experimental realization of high Tc superconductivity in calcium superhydrides synthesized at high pressure and high temperature conditions.…”

Section: Introductionmentioning

confidence: 95%

Superconductivity above 200K Observed in Superhydrides of Calcium

Zhang

et al. 2021

Preprint

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Searching for superconductivity with Tc near room temperature is of great interest both for fundamental science & potential applications. Here we report the experimental discovery of superconductivity with maximum critical temperature(Tc) above 210 K in calcium superhydrides, the third type hydride experimentally showing superconductivity above 200K in addition to sulfur hydride & rare earth hydride system. The materials are synthesized at the synergetic conditions of 160~190 GPa and ~2000K using diamond anvil cell combined with in-situ laser heating technique. The superconductivity was studied through in situ high pressure resistance measurements in applied magnetic field for the sample quenched from high temperature while maintained at the synthesized pressure. The upper critical field was estimated to be ~268T while the GL coherent length is ~11 Å. The in situ x ray diffractions with synchrotron suggest that the synthesized calcium hydrides are primarily composed of CaH6 while there also exist other calcium hydrids with different hydrogen.

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Synthesis of molecular metallic barium superhydride: pseudocubic BaH12

Cited by 96 publications

References 59 publications

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Chemical templates that assemble the metal superhydrides

Superconductivity above 200K Observed in Superhydrides of Calcium

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