Structure of 'orange' <sup>18</sup>O<sub>2</sub> at 9.6 GPa and 297 K

Schiferl, D.; Cromer, D. T.; Schwalbe, L.A.; Mills, R. L.

doi:10.1107/s0108768183002219

Cited by 72 publications

(33 citation statements)

References 16 publications

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“…In changing the molecular volume V M , we fixed the mutual ratio of the lattice constants and the angle of the monoclinic structure to the values determined from the experiments. [61][62][63] Furthermore, the intramolecular atomic distance was maintained at 1.2…”

Section: Metallization Of Oxygen Under Pressurementioning

confidence: 99%

Pressure-induced Superconductivity in Elemental Materials

2005

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Both experimental and theoretical approaches in our search for superconductivity under pressure are reviewed. We have developed a double extreme condition of very low-temperature down to 50 mK using a 3 He/ 4 He dilution refrigerator and ultrahigh pressure up to 200 GPa using a diamond-anvil cell (DAC). Experimental techniques producing ultrahigh pressure as well as measuring electrical resistance, magnetization and optical response are developed especially for studying the pressure-induced superconductivity of simple systems such as elemental materials. The details of these techniques are described in §1. In §2, we review several examples of pressure-induced superconductivity observed for the first time by our group. Comparisons between experimental results and theories based on the first principles band calculations are given in §3. Finally, we point out remaining problems to be solved in further studies in the search for pressure-induced superconductivity.

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Section: Metallization Of Oxygen Under Pressurementioning

confidence: 99%

Pressure-induced Superconductivity in Elemental Materials

2005

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“…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)(7)(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).…”

mentioning

confidence: 99%

Spiral chain O ₄ form of dense oxygen

Zhu

Wang

et al. 2012

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

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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“…The patterns measured at 7.0 and 6.6 GPa are unequivocally assigned to an orthorhombic cell, having the Fmmm space group, the same as found at 9.6 GPa at ambient temperature. 8 At 5.8 GPa the 200 line is strongly shifted to lower angle and the 111 line is split into 111 and 111. This is unambiguous evidence of the transition to the monoclinic phase.…”

Section: Structural Investigationmentioning

confidence: 99%

“…The υ phase is orthorhombic face centred (Fmmm) with one molecule in the primitive cell. 8 All these phases, with the exception of the phase, are characterized by a layered structure with the oxygen molecules perpendicular to a crystal plane and with the centres of mass lying on the same plane. In these phases solid oxygen can be considered as a two-dimensional system and the intermolecular potential energy is dominated by the in-plane interactions.…”

Section: Introductionmentioning

confidence: 99%

High‐pressure antiferromagnetic phases of solid oxygen

Gorelli¹,

Santoro²

2003

J Raman Spectroscopy

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We report on the antiferromagnetic character of solid oxygen in the high-pressure, low-temperature region enclosed between the b and e phases. The occurrence of a first-order phase transition, positioned at 5.5-6.5 GPa, between the monoclinic a (C2/m) and the orthorhombic d (Fmmm) phases was shown by means of an accurate x-ray diffraction analysis. The two crystal structures were assessed to be antiferromagnetically ordered, owing to a narrow peak observed in the IR spectrum and assigned to a vibron component. The absorption of this mode is allowed owing to the coupling of the molecular spins, which produces a doubling of the primitive cell. The vibrational coupling parameter was quantitatively related to the exchange integral J involved in the Heisenberg interaction. Finally, absorption measurements at different pressures of the electronic transition 3 6 − g → 1 1 g , lying in the near-IR spectral range, allowed us, by means of a simple model, to obtain directly the quantity J as a function of the nearest-neighbour distance.

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Structure of 'orange' ¹⁸O₂ at 9.6 GPa and 297 K

Cited by 72 publications

References 16 publications

Pressure-induced Superconductivity in Elemental Materials

Pressure-induced Superconductivity in Elemental Materials

Spiral chain O ₄ form of dense oxygen

High‐pressure antiferromagnetic phases of solid oxygen

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Structure of 'orange' 18O2 at 9.6 GPa and 297 K

Cited by 72 publications

References 16 publications

Pressure-induced Superconductivity in Elemental Materials

Pressure-induced Superconductivity in Elemental Materials

Spiral chain O 4 form of dense oxygen

High‐pressure antiferromagnetic phases of solid oxygen

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Structure of 'orange' ¹⁸O₂ at 9.6 GPa and 297 K

Spiral chain O ₄ form of dense oxygen