Pushing Towards Room-Temperature Superconductivity

Zurek, Eva

doi:10.1103/physics.12.1

Cited by 6 publications

(7 citation statements)

References 27 publications

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“…The curious absence of superconductivity in seemingly promising MH n materials is considered in Section 3.1 from the perspective of charge balance, disorder, and phase purity. The suppressed T C reported for fcc LaD 10 in determining the H-D isotope effect [12] is considered in Section 3.2 in terms of materials issues [36], which are shown to be relevant for interpreting the T C of D 3 S [42] and the oxygen isotope effect in high-T C cuprates [68][69][70]. A study to detect the signature of the charge transfer potential e 2 /ζ embedded in Eq.…”

Section: Discussionmentioning

confidence: 99%

“…A review of conventional electron-phonon coupling theory in [4] includes a listing of numerous computational flaws that remain to be addressed. 1 As independent corroboration of phonon mediation has yet to be convincingly established [36], alternative considerations of electronic mechanisms are being developed, particularly in view of the high pressures [37], correspondences to high-T C cuprates [38] and limitations on the Fermi temperatures [39].…”

Section: Introductionmentioning

confidence: 99%

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High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

Harshman

Fiory

2020

J Supercond Nov Magn

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The uniquely characteristic macrostructures of binary hydrogen-clathrate compounds MH n formed at high pressure, a cage of hydrogens surrounding a central-atom host, is theoretically predicted in various studies to include structurally stable phonon-mediated superconductors. High superconductive transition temperatures T C have thus far been measured for syntheses with M = La, Y, and Th. In compressed LaH 10 , independent studies report T C of 250 K and over 260 K, a maximum in T C with pressure P, and normal-state resistance scaling with temperature (suggesting unconventional pairing). According to reported band structure calculations of Fm m-phase LaH 10 , the La is anionic, with the chemical valence electrons appearing evenly split between La and H 10 . Thus, compressed LaH 10 contains the combination of structure, charge separation and optimal balanced allocation of valence electrons for supporting unconventional high-T C superconductivity mediated by Coulomb interactions between electronic charges associated with La and H 10 . A general expression for the optimal superconducting transition temperature for MH n clathrates is derived as T C0 = k B 1 [(n + v)/2A] 1/2 e 2 /ζ, where  is a universal constant, (n + v) is the chemical valence sum per formula unit, taking unity for H and v for atom M, A is the surface area of the H-polyhedron cage, and  is the mean distance between the M site and the centroids of the polyhedron faces. Applied to Fm m LaH 10 , T C0 values of 249.8(1.3) K and 260.7(2.0) K are found for the two experiments. Associated attributes of charge allocation, structure, effective Coulomb potential, and H-D isotope effect in T C of Fm m LaH 10 and Im m H 3 S are discussed, along with a generalized prospective for Coulomb-mediated superconductivity in MH n . 1 The layered FeH 5 , synthesized with no demonstration of superconductivity [32], is predicted to be superconducting in [33,34] and non-superconducting in [35]. 2 Note that here is a typographical error at the end of Section 3 (p. 5) of [41] which should read, "ℓ = (A/) 1/2 = 2.88 Å," with the reported T C0 remaining unchanged.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

Harshman

Fiory

2020

J Supercond Nov Magn

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“…[73,74] Significantly, these cage-like structures can also become hosts for superconducting materials. More recent experiments reported a superhydride, LaH 10 , with a superconducting transition temperature (T c ) close to room temperature [75][76][77] and a structure reminiscent of the cage-like f cc-C 32 carbon. The P carbon (Fig.…”

Section: -2mentioning

confidence: 99%

“…[73,74] Notably, the predicted fcc-C 32 (e) has the same structure with recently synthesized LaH 10 possessing T c near room temperature at high pressure. [75][76][77] (f) A type of microporous carbon form. [78] Table 1.…”

Section: -2mentioning

confidence: 99%

Discovery of superhard materials via CALYPSO methodology*

Zhang

Zhao

et al. 2019

Chinese Phys. B

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The study of superhard materials plays a critical role in modern industrial applications due to their widespread applications as cutting tools, abrasives, exploitation drills, and coatings. The search for new superhard materials with superior performance remains a hot topic and is mainly considered as two classes of materials: (i) the light-element compounds in the B–C–N–O(–Si) system with strong and short covalent bonds, and (ii) the transition-element light-element compounds with strong covalent bonds frameworks and high valence electron density. In this paper, we review the recent achievements in the prediction of superhard materials mostly using the advanced CALYPSO methodology. A number of novel, superhard crystals of light-element compounds and transition-metal borides, carbides, and nitrides have been theoretically identified and some of them account well for the experimentally mysterious phases. To design superhard materials via CALYPSO methodology is independent of any known structural and experimental data, resulting in many remarkable structures accelerating the development of new superhard materials.

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“…Another hydride with a nontraditional stoichiometry that was predicted prior to its synthesis , is the I 4/ mmm symmetry CaH 4 phase shown in Figure d, which contains both molecular and atomic hydrogen. The structures and propensity for superconductivity of most binary hydrides have been theoretically studied under pressure. − …”

Section: Introductionmentioning

confidence: 99%

The XtalOpt Evolutionary Algorithm for Crystal Structure Prediction

et al. 2020

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Significant progress has been made in the field of a priori crystal structure prediction, with a number of recent remarkable success stories. Herein, we briefly outline the methods that have been developed for finding the global minimum structure and interesting local minima without the need for experimental information. Focus is placed on describing the XtalOpt evolutionary algorithm (EA) developed in our group toward this end. XtalOpt is published under well-known open-source licenses, and the EA searches can be analyzed via the Avogadro chemical editor and visualizer. We describe new algorithmic developments that have made it possible to predict the structures of ever-more complex crystalline lattices. Benchmark tests, which clearly illustrate how the new developments improve the success rate and accelerate the discovery of the global minimum structure, are performed. Finally, we describe how XtalOpt has been employed to predict novel ternary hydrides that have the propensity for high-temperature superconductivity under pressure.

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Pushing Towards Room-Temperature Superconductivity

Cited by 6 publications

References 27 publications

High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

High-TC Superconductivity in Hydrogen Clathrates Mediated by Coulomb Interactions Between Hydrogen and Central-Atom Electrons

Discovery of superhard materials via CALYPSO methodology*

The XtalOpt Evolutionary Algorithm for Crystal Structure Prediction

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