Synthesis of Weaire–Phelan Barium Polyhydride

Peña-Álvarez, Miriam; Binns, Jack; Martínez-Canales, Miguel; Monserrat, Bartomeu; Ackland, Graeme; Dalladay‐Simpson, Philip; Howie, Ross T.; Pickard, Chris J.; Gregoryanz, Eugene

doi:10.1021/acs.jpclett.1c00826

Cited by 19 publications

(28 citation statements)

References 51 publications

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“…The observed X-ray diffraction pattern (Figure 2a,b) with main reflections (200), (210), and (211) corresponds to the 3 Pm n structure found earlier in the studies of europium (Eu 8 H 46 [24] ) and barium (Ba 8 H 46 [25] ) polyhydrides. However, both the harmonic and anharmonic calculations show dynamical instability at 300 K of structurally similar cubic strontium hydride Sr 8 H 46 , which distorts to R c 3 having a significantly different XRD pattern.…”

Section: High-pressure Synthesis Of Pseudocubic Srhsupporting

confidence: 72%

“…An evolutionary search using USPEX for thermodynamically stable phases in the SrH system ( Figure , and Figures S1 and S2, Supporting Information) shows that this system is very rich in various compounds. At 150 GPa and 0 K (Figure 1f), there are several strontium hydrides on the convex hull: well‐known P 6/ mmm‐ SrH 2 ; pseudocubic P 1‐SrH 6 (or Sr 8 H 48 ) similar to recently discovered Eu 8 H 46 [ 24 ] and Ba 8 H 46 ; [ 25 ] superhydrides C 2 /m‐ SrH 10 and P 1‐SrH 17 . At 100 GPa (Figure 1c), lower hydrides Cmmm‐ SrH and Cmcm‐ SrH 4 are stable, as well as Sr 8 H 48 and superhydride P 1‐SrH 22 , whose structure is described below.…”

Section: Resultsmentioning

confidence: 77%

“…A better organized structure of P1-SrH 6 , which is close to the cubic prototypes Pm n 3 -Eu 8 H 46 [24] and Ba 8 H 46 , [25] is more stable than the disordered molecular hydride SrH 22 , where individual hydrogen atoms and molecules can migrate to a neighboring unit cell within 1 ns. This surprising fact is confirmed by the radial distribution functions (Figures S39-S45, Supporting Information): both strontium hydrides have a glassy disordered H sublattice and a solid Sr sublattice, stabilized due to the interaction of coordination shells [SrH 24 ] at 300-600 K and 150 GPa.…”

Section: Electrical Measurements Of Srhmentioning

confidence: 94%

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Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

et al. 2022

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experimental metallization limit moving step by step from 150 [4] to 430-500 GPa. [1,5] A consistent increase in pressure leads to a series of phase transitions in solid hydrogen (phases Ι-V [1,5] ), gradual quenching of the Raman signals, and darkening of the sample down to a complete loss of transparency. Despite a significant progress in achieving ultrahigh pressures in the last five years, detecting superconductivity of metallic hydrogen remains an unsolved problem. Studies of the electrical conductivity at pressures above 400 GPa remain very challenging.In 2004, N. Ashcroft suggested that the precompression effects caused by chemical bonding to other atoms may help to convert hydrogen to a metallic state. Fifteen years later, this idea was confirmed in the synthesis of many metallic and superconducting hydrides such as H 3 S, [6,7] LaH 10 , [8,9] YH 6 , [10,11] YH 9 , [11,12] ThH 10 , [13] CeH 9 , [14] PrH 9 , [15] NdH 9 , [16] and so forth. It is believed now that the superconducting properties of these compounds are due to the presence of a sublattice of metallic hydrogen, which is formed in pure hydrogen only at pressures of 500-700 GPa.There must be an intermediate link between these two forms of hydrogen, metallic and superconducting, and a molecular Recently, several research groups announced reaching the point of metallization of hydrogen above 400 GPa. Despite notable progress, detecting superconductivity in compressed hydrogen remains an unsolved problem. Following the mainstream of extensive investigations of compressed metal polyhydrides, here small doping of molecular hydrogen by strontium is demonstrated to lead to a dramatic reduction in the metallization pressure to ≈200 GPa. Studying the high-pressure chemistry of the Sr-H system, the formation of several new phases is observed: C2/m-Sr 3 H 13 , pseudocubic SrH 6 , SrH 9 with cubic F m 43 -Sr sublattice, and pseudo tetragonal superionic P1-SrH 22 , the metal hydride with the highest hydrogen content (96 at%) discovered so far. High diffusion coefficients of hydrogen in the latter phase D H = 0.2-2.1 × 10 −9 m 2 s −1 indicate an amorphous state of the H-sublattice, whereas the strontium sublattice remains solid. Unlike Ca and Y, strontium forms molecular semiconducting polyhydrides, whereas calcium and yttrium polyhydrides are high-T C superconductors with an atomic H sublattice. The discovered SrH 22 , a kind of hydrogen sponge, opens a new class of materials with ultrahigh content of hydrogen.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202200924.

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Section: High-pressure Synthesis Of Pseudocubic Srhsupporting

confidence: 72%

Section: Resultsmentioning

confidence: 77%

Section: Electrical Measurements Of Srhmentioning

confidence: 94%

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Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

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“…CaH 4 , SrH 4 , and BaH 4 are refined to tetragonal I 4/ mmm at 52, 44, and 45 GPa, respectively. Upon decompression, I 4/ mmm BaH 4 (and Ba 8 H 46 ) 30 undergoes a phase transition to BaH 4 . (b) Volume per alkaline-earth atom as a function of pressure.…”

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confidence: 99%

Chemically Assisted Precompression of Hydrogen Molecules in Alkaline-Earth Tetrahydrides

Peña-Álvarez

Binns

Marqués

et al. 2022

J. Phys. Chem. Lett.

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Through a series of high pressure diamond anvil experiments, we report the synthesis of alkaline earth (Ca, Sr, Ba) tetrahydrides, and investigate their properties through Raman spectroscopy, X-ray diffraction, and density functional theory calculations. The tetrahydrides incorporate both atomic and quasi-molecular hydrogen, and we find that the frequency of the intramolecular stretching mode of the units downshifts from Ca to Sr and to Ba upon compression. The experimental results indicate that the larger the host cation, the longer the bond. Analysis of the electron localization function (ELF) demonstrates that the lengthening of the H–H bond is caused by the charge transfer from the metal to and by the steric effect of the metal host on the H–H bond. This effect is most prominent for BaH 4 , where the precompression of units at 50 GPa results in bond lengths comparable to that of pure H 2 above 275 GPa.

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“…One of the effective approaches to search for their structures is compare them with those of known binary intermetallides formed by atoms with significantly different radii. Such an approach was successfully applied in the theoretical study of clathrate Li2MgH16 (predicted TC up to 473 K [32]) and in the experimental discovery of Eu8H46 [43] and Ba8H46 [80], which have a large number of prototypes such as Ba4Si23, Ba4Ge23, Cs4Sn23, etc.…”

Section: Methods For Studying Metal Polyhydridesmentioning

confidence: 99%

High-temperature superconductivity in hydrides

et al. 2021

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Over the past six years (2015)(2016)(2017)(2018)(2019)(2020)(2021), many superconducting hydrides with critical temperatures TC up to 250 K, which are currently record highs, have been discovered. Now we can already say that a special field of superconductivity has developed. This is hydride superconductivity at ultrahigh pressures. For the most part, the properties of superhydrides are well described by the Migdal-Eliashberg theory of strong electronphonon interaction, especially when anharmonicity of phonons is taken into account. We investigate the isotope effect, the effect of the magnetic field (up to 60-70 T) on the critical temperature and critical current in the hydride samples, and the dependence of Tc on the pressure and the degree of doping. The divergences between the theory and experiment are of interest, especially in the regions of phase stability and in the behavior of the upper critical magnetic fields at low temperatures. We present a retrospective analysis of data of 2015-2021 and describe promising directions for future research of hydride superconductivity.

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Synthesis of Weaire–Phelan Barium Polyhydride

Cited by 19 publications

References 51 publications

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

Chemically Assisted Precompression of Hydrogen Molecules in Alkaline-Earth Tetrahydrides

High-temperature superconductivity in hydrides

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Synthesis of Weaire–Phelan Barium Polyhydride

Cited by 19 publications

References 51 publications

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH22

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH22

Chemically Assisted Precompression of Hydrogen Molecules in Alkaline-Earth Tetrahydrides

High-temperature superconductivity in hydrides

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Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂