Theoretical study of stability and superconductivity of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>ScH</mml:mi><mml:mi>n</mml:mi></mml:msub></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn>4</mml:mn><mml:mo>–</mml:mo><mml:mn>8</mml:mn></mml:mrow></mml:math>) at high pressure

Qian, Shifeng; Sheng, Xiaowei; Yan, Xiaozhen; Chen, Yangmei; Song, Bo

doi:10.1103/physrevb.96.094513

“…. Theoretical studies based upon a priori crystal structure prediction have found that MgH 4 , [30] CaH 4 , [31][32][33] SrH 4 , [34,35] ScH 4 , [18,[36][37][38] YH 4 , [18] ZrH 4 , [30] LaH 4 , [19] CeH 4 , [18,39,40] PrH 4 , [18] NdH 4 , [41] EuH 4 , [42] TbH 4 , [43] ThH 4 , [44] PuH 4 , [45] and all of the REH 4 [29] phases assuming this structure type are thermodynamically stable in their respective pressure ranges. Therefore, this I4=mmm structure may be a universal feature in the phase diagram of most of the compressed alkaline and rare earth, as well as a few transition metal and actinide tetrahydrides under pressure.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Bi

¹

,

Zurek

²

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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“…Intriguingly, five different lines intersect at ScYH 6 in Figure 1B, suggesting that this compound could be obtained via five different synthesis routes based on TSLM, that is, ScH 6 + Y → ScYH 6 , Sc + YH 6 → ScYH 6 , ScH 2 + YH 4 → ScYH 6 , ScH 3 + YH 3 → ScYH 6 , and ScH 4 + YH 2 → ScYH 6 . However, it should be noticed that cP8‐ScYH 6 could only be synthesized through ScH 3 + YH 3 → ScYH 6 under a low‐pressure regime (0‐100 GPa) because ScH 4 and ScH 6 are dynamically stable when pressures are above 150 and 100 GPa, [ 49,50 ] respectively. On the other hand, YH 4 and YH 6 also exist when pressure is above 100 GPa.…”

Section: Resultsmentioning

confidence: 98%

“…Several reports have conducted comprehensive investigations, and our predictions also agree well with relative work, such as Fm‐3m‐ScH 2 , Fm‐3m and Pm‐3m‐ScH 3 , I4/mmm‐ScH 4 , Im‐3m‐ScH 6 , Fm‐3m‐YH 2 , Fm‐3m‐YH 3 , I4/mmm‐YH 4 , Fm‐3m‐YH 6 , and so on. [ 13,14,48–50 ] Besides, we have also carefully studied the superconductivity and electronic structures of scandium hydrides under pressures before. [ 48 ] For each simple substance and hydride, the most stable structure was applied to obtain the enthalpy under corresponding pressure.…”

Section: Resultsmentioning

confidence: 99%

Formation and superconducting properties of predicted ternary hydride ScYH₆ under pressures

Wei

¹

,

Jia

²

,

Fang

³

et al. 2020

Int J of Quantum Chemistry

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Ternary metal hydrides play an essential role in the search for conventional high‐temperature superconductors because they can be synthesized under mild conditions and recovered at ambient pressure. It has been widely accepted that the electronic structure, metallization pressure, and superconducting behavior of binary hydrides can be adjusted effectively by doping, replacing, or introducing a new element. In this work, yttrium hydrides were chosen as parent hydrides, while scandium was considered the doping element to perform systematical crystal structure searches on the Sc‐Y‐H system under pressure. A new ternary hydride ScYH6 with a Pm‐3 structure (cP8) was found below 150 GPa according to Particle Swarm Optimization calculations, and then, a P4/mmm phase (tP8) becomes favorable from 150 GPa. Importantly, cP8‐ScYH6 is dynamically stable under pressure as low as 0.01 GPa with a superconducting temperature (Tc) of 32.110 K for Coulomb pseudopotential μ* = 0.13, indicating that ternary hydrides are promising candidates in the search for superconductors that can be synthesized under mild conditions in hydrogen‐rich materials. The analysis using the “triangle straight‐line method”, compared with enthalpy difference calculations, showed that the most reasonable synthesis pathway of ScYH6 is ScH3 + YH3 → ScYH6 in the whole pressure regime studied in this work. The Tc of ScYH6 has a linear relationship with pressure up to 52.907 K under 200 GPa. The lattice dynamical calculations demonstrate that the H atoms in both cP8 and tP8 structures make crucial contributions to the superconducting behavior of ScYH6. These findings can further reveal the influence of doping, replacing, and introducing element on the superconducting behavior of binary hydrides.

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“…Among the predicted the value of , based on the Allen–Dynes equation 32 . In 2017, was predicted the high- above 100 K from 300 to 400 GPa 33 . In the same year, was investigated by using the first-principles calculations, carried out the McMillan formula with Allen-Dynes corrections 32 , 34 .…”

Section: Introductionmentioning

confidence: 99%

High-temperature superconductor of sodalite-like clathrate hafnium hexahydride

Tsuppayakorn‐aek

¹

,

Phaisangittisakul

²

,

Ahuja

³

et al. 2021

Sci Rep

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Hafnium hydrogen compounds have recently become the vibrant materials for structural prediction at high pressure, from their high potential candidate for high-temperature superconductors. In this work, we predict $$\hbox {HfH}_{6}$$ HfH 6 by exploiting the evolutionary searching. A high-pressure phase adopts a sodalite-like clathrate structure, showing the body-centered cubic structure with a space group of $$Im\bar{3}m$$ I m 3 ¯ m . The first-principles calculations have been used, including the zero-point energy, to investigate the probable structures up to 600 GPa, and find that the $$Im\bar{3}m$$ I m 3 ¯ m structure is thermodynamically and dynamically stable. This remarkable result of the $$Im\bar{3}m$$ I m 3 ¯ m structure shows the van Hove singularity at the Fermi level by determining the density of states. We calculate a superconducting transition temperature ($$T_{c}$$ T c ) using Allen-Dynes equation and demonstrated that it exhibits superconductivity under high pressure with relatively high-$$T_{c}$$ T c of 132 K.

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Theoretical study of stability and superconductivity ofScHn(n=4–8) at high pressure

Cited by 48 publications

References 45 publications

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Formation and superconducting properties of predicted ternary hydride ScYH₆ under pressures

High-temperature superconductor of sodalite-like clathrate hafnium hexahydride

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Theoretical study of stability and superconductivity ofScHn(n=4–8) at high pressure

Cited by 48 publications

References 45 publications

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Electronic Structure and Superconductivity of Compressed Metal Tetrahydrides

Formation and superconducting properties of predicted ternary hydride ScYH6 under pressures

High-temperature superconductor of sodalite-like clathrate hafnium hexahydride

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Formation and superconducting properties of predicted ternary hydride ScYH₆ under pressures