Substitutional Alloy of Bi and Te at High Pressure

Zhu, Li; Wang, Hui; Wang, Yanchao; Lv, Jian; Ma, Yiming; Cui, Qiliang; Ma, Yanming; Zou, Guangtian

doi:10.1103/physrevlett.106.145501

Cited by 384 publications

(348 citation statements)

References 18 publications

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“…Our CALYPSO method unbiased by any known structural information has been benchmarked on various known systems 19 with various chemical bondings and had several successful prediction of high-pressure structures of Li, Mg, and Bi 2 Te 3 (30-32), among which the insulating orthorhombic (Aba2, Pearson symbol oC40) structure of Li and the two low-pressure monoclinic structures of Bi 2 Te 3 have been confirmed by independent experiments (32,33). The underlying ab initio structural relaxations were carried out using density functional theory within the Perdew-Burke-Ernzerhof exchange-correlation (34) as implemented in the Vienna Ab Initio Simulation Package (VASP) code (35).…”

Section: Methodsmentioning

confidence: 96%

Superconductive sodalite-like clathrate calcium hydride at high pressures

Wang

Tse

Tanaka

et al. 2012

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

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752

676

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Hydrogen-rich compounds hold promise as high-temperature superconductors under high pressures. Recent theoretical hydride structures on achieving high-pressure superconductivity are composed mainly of H 2 fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particleswam optimization structural search, we show that in the stoichiometry CaH 6 a body-centered cubic structure with hydrogen that forms unusual "sodalite" cages containing enclathrated Ca stabilizes above pressure 150 GPa. The stability of this structure is derived from the acceptance by two H 2 of electrons donated by Ca forming an "H 4 " unit as the building block in the construction of the three-dimensional sodalite cage. This unique structure has a partial occupation of the degenerated orbitals at the zone center. The resultant dynamic Jahn-Teller effect helps to enhance electronphonon coupling and leads to superconductivity of CaH 6 . A superconducting critical temperature (T c ) of 220-235 K at 150 GPa obtained from the solution of the Eliashberg equations is the highest among all hydrides studied thus far.calcium hydride | sodalite structure

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Section: Methodsmentioning

confidence: 96%

Superconductive sodalite-like clathrate calcium hydride at high pressures

Wang

Tse

Tanaka

et al. 2012

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

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752

676

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“…31 This method has been benchmarked on a variety of known systems and has made several successful predictions of high pressure structures of, for example, Li, Mg, and Bi 2 Te 3 . [32][33][34] Our structure searches with system sizes containing up to 8 formula units (f.u.) per simulation cell were performed at pressures of 15-400 GPa.…”

Section: Computational Detailsmentioning

confidence: 99%

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

et al. 2013

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As part of a search for enhanced superconductivity, we explore theoretically the ground-state structures and properties of some hydrides of niobium over a range of pressures and particularly those with significant hydrogen content. A primary motivation originates with the observation that under normal conditions niobium is the element with the highest superconducting transition temperature (T c ), and moreover some of its compounds are metals again with very high T c 's. Accordingly, combinations of niobium with hydrogen, with its high dynamic energy scale, are also of considerable interest. This is reinforced further by the suggestion that close to its insulator-metal transition, hydrogen may be induced to enter the metallic state somewhat prematurely by the addition of a relatively small concentration of a suitable transition metal. Here, the methods used correctly reproduce some ground-state structures of niobium hydrides at even higher concentrations of niobium. Interestingly, the particular stoichiometries represented by NbH 4 and NbH 6 are stabilized at fairly low pressures when proton zero-point energies are included. While no paired H 2 units are found in any of the hydrides we have studied up to 400 GPa, we do find complex and interesting networks of hydrogens around the niobiums in high-pressure NbH 6 . The Nb-Nb separations in NbH n are consistently larger than those found in Nb metal at the respective pressures. The structures found in the ground states of the high hydrides, many of them metallic, suggest that the coordination number of hydrogens around each niobium atom grows approximately as 4n in NbH n (n = 1-4), and is as high as 20 in NbH 6 . NbH 4 is found to be a plausible candidate to become a superconductor at high pressure, with an estimated T c ∼ 38 K at 300 GPa.

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“…Our CALYPSO method has been implemented in the CALYPSO code and successfully benchmarked on a number of known systems (22). Several predictions of high-pressure structures of dense Li, Mg, Bi 2 Te 3 , and water ice (23)(24)(25)(26) were successfully made, and predictions of the high-pressure insulating Aba2-40 (Pearson symbol oC40) structure of Li and the two low-pressure monoclinic structures of Bi 2 Te 3 were confirmed by independent experiments (25,27).…”

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confidence: 91%

Spiral chain O ₄ form of dense oxygen

Zhu

Wang

et al. 2012

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

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112

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Oxygen is in many ways a unique element: It is the only known diatomic molecular magnet, and it exhibits an unusual O 8 cluster in its high-pressure solid phase. Pressure-induced molecular dissociation as one of the fundamental problems in physical sciences has been reported from theoretical or experimental studies of diatomic solids H 2 , N 2 , F 2 , Cl 2 , Br 2 , and I 2 but remains elusive for molecular oxygen. We report here the prediction of the dissociation of molecular oxygen into a polymeric spiral chain O 4 structure (space group I4 1 ∕acd, θ-O 4 ) above 1.92-TPa pressure using the particleswarm search method. The θ-O 4 phase has a similar structure as the high-pressure phase III of sulfur. The molecular bonding in the insulating ε-O 8 phase or the isostructural superconducting ζ-O 8 phase remains remarkably stable over a large pressure range of 0.008-1.92 TPa. The pressure-induced softening of a transverse acoustic phonon mode at the zone boundary V point of O 8 phase might be the ultimate driving force for the formation of θ-O 4 . Stabilization of θ-O 4 turns oxygen from a superconductor into an insulator by opening a wide band gap (approximately 5.9 eV) that originates from the sp 3 -like hybridized orbitals of oxygen and the localization of valence electrons.solid oxygen | spiral chain structure A s a long-standing problem in physics and chemistry, as well as earth and planetary sciences, high-pressure dissociation of diatomic molecules, such as H 2 , N 2 , O 2 , F 2 , Cl 2 , Br 2 , and I 2 , has attracted a lot of attention. Among these molecular systems, solid oxygen is a system of particular interest and exhibits many unusual physical properties by virtue of its molecular spin and the resultant spin-spin interactions, which make the system a critical test case for condensed-matter theory (1, 2). Oxygen is also the third most abundant element in the Solar System, and its behavior under extreme pressures provides important insight into the oxygen-related systems for a better understanding of the physics and chemistry of planetary interiors.Oxygen exhibits a rich polymorphism with seven unambiguously established crystalline phases. Upon cooling at ambient pressure, oxygen is in turn solidified to the paramagnetic γ-phase, the magnetically disordered (short-range ordered) β-phase (3, 4), and ultimately the antiferromagnetic α-phase (5). Upon compressing to approximately 6 GPa, the α-phase transforms into the antiferromagnetic δ-phase (6-8). Under a higher pressure of approximately 8 GPa, the magnetic order of oxygen is destroyed, which leads to the ε-O 8 phase consisting of O 8 clusters (9, 10). The ε-O 8 phase displays the bonding characteristics of a closedshell system, in which the intermolecular interactions primarily involve the half-filled 1π g Ã orbital of O 2 (11). Above 96 GPa, ε-O 8 has been observed to transform into a metallic ζ-phase (12, 13) and intriguingly exhibits superconductivity with a transition temperature of 0.6 K (14). This superconducting ζ-phase has been predicted by theory ...

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Substitutional Alloy of Bi and Te at High Pressure

Cited by 384 publications

References 18 publications

Superconductive sodalite-like clathrate calcium hydride at high pressures

Superconductive sodalite-like clathrate calcium hydride at high pressures

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

Spiral chain O ₄ form of dense oxygen

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Substitutional Alloy of Bi and Te at High Pressure

Cited by 384 publications

References 18 publications

Superconductive sodalite-like clathrate calcium hydride at high pressures

Superconductive sodalite-like clathrate calcium hydride at high pressures

Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

Spiral chain O 4 form of dense oxygen

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Spiral chain O ₄ form of dense oxygen