New High-Pressure Structural Transition of Oxygen at 96 GPa Associated with Metallization in a Molecular Solid

Akahama, Yuichi; Kawamura, Haruki; Häusermann, Daniel M.; Hanfland, Michael; Shimomura, Osamu

doi:10.1103/physrevlett.74.4690

Cited by 180 publications

(111 citation statements)

References 21 publications

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“…Although there is some scatter in the region of the -phase, the overall variation can be largely accounted for by the volume change, providing evidence that the variation in the * transition energy is a consequence of the expected volume reduction under pressure. The decreased variation in the * transition energy Ͼ10 GPa is consistent with the low compressibility of the -phase as determined by x-ray diffraction (3,5). The contrasting behavior of the * and * transition energies indicates the involvement of the 1 g * molecular orbitals on adjacent O 2 molecules, an interaction which evolves as oxygen undergoes phase transitions at high pressure.…”

Section: Resultssupporting

confidence: 51%

Inelastic x-ray scattering of dense solid oxygen: Evidence for intermolecular bonding

Meng

Eng

Tse

et al. 2008

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

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The detailing of the intermolecular interactions in dense solid oxygen is essential for an understanding of the rich polymorphism and remarkable properties of this element at high pressure. Synchrotron inelastic x-ray scattering measurements of oxygen K-edge excitations to 38 GPa reveal changes in electronic structure and bonding on compression of the molecular solid. The measurements show that O 2 molecules interact predominantly through the half-filled 1π g * orbital <10 GPa. Enhanced intermolecular interactions develop because of increasing overlap of the 1π g * orbital in the low-pressure phases, leading to electron delocalization and ultimately intermolecular bonding between O 2 molecules at the transition to the ε-phase. The ε-phase, which consists of (O 2 ) 4 clusters, displays the bonding characteristics of a closed-shell system. Increasing interactions between (O 2 ) 4 clusters develop upon compression of the ε-phase, and provide a potential mechanism for intercluster bonding in still higher-pressure phases.

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Section: Resultssupporting

confidence: 51%

Inelastic x-ray scattering of dense solid oxygen: Evidence for intermolecular bonding

Meng

Eng

Tse

et al. 2008

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

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“…They found for ε-O 2 the based-centered monoclinic lattice of space group A2=m with 8 molecules in the unit cell. This space group was later confirmed in powder X-ray diffraction experiments performed on samples of pure oxygen [40,41]. In one of this study, conducted by Akahama et al [41] at the very beginning of the user operation at the ESRF synchrotron source, the diffraction lines were followed up to above the metallization.…”

Section: The ε Phasementioning

confidence: 86%

X-ray crystallography of simple molecular solids up to megabar pressures: application to solid oxygen and carbon dioxide

Datchi

Weck

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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A review of recently developed methods to study the structural properties of simple molecular solids under pressures up to the megabar range using synchrotron X-ray diffraction techniques is presented. This includes the growth of single-crystals at high pressure and temperature conditions and the use of He as pressuretransmitting medium. The application of these methods to solid O 2 and CO 2 is then presented as illustrative examples, showing how they enabled to solve long-standing debates on the structure of the high-pressure crystalline phases of these compounds.

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“…In the fluid we observe a Mott transition where density driven band closure and disorder play the fundamental roles. In the solid, on the other hand, the metallization is associated with a structural phase transition [14].…”

mentioning

confidence: 99%

“…Oxygen has very rich physics at high pressure. Since dramatic color changes were reported in the 100kbar pressure range [12], the high pressure solid phases of oxygen have been extensively investigated using structural [13][14][15], optical [7,8] and transport techniques [9]. A metallic state and evidence for superconductivity have been identified in the solid around 1M bar at very low temperatures [8,9].…”

mentioning

confidence: 99%

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

2001

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We report the first experimental evidence for a metallic phase in fluid molecular oxygen. Our electrical conductivity measurements of fluid oxygen under dynamic quasi-isentropic compression show that a non-metal/metal transition occurs at 3.4 fold compression, 4500 K and 1.2 Mbar. We discuss the main features of the electrical conductivity dependence on density and temperature and give an interpretation of the nature of the electrical transport mechanisms in fluid oxygen at these extreme conditions. PACS numbers: 71.30.+h, 62.50.+p, 77.22.Ej The transition of condensed matter between electrically conducting and insulating states is a topic of wide scientific interest, whose relevance ranges from superconductivity to collosal magnetoresistance [1], to more recently thermoelectricity [2]. The metal/insulator transition has received renewed attention during the past decade in the context of high pressure research [3]. Although much progress has been made in developing experimental, theoretical and computational tools appropriate for the study of the metal/insulator transition at extreme conditions, our present understanding is mostly phenomenological and still incomplete. Given the "simple" nature of their interactions, the homonuclear diatomic molecular species, e.g. hydrogen [4][5][6], oxygen [7][8][9], nitrogen [10] and the halogens [11], have been intensively studied using both static and dynamic high pressure techniques.We report in this letter the first experimental evidence for a non-metal/metal transition in the molecular fluid phase of oxygen under high dynamic compression. Oxygen has very rich physics at high pressure. Since dramatic color changes were reported in the 100kbar pressure range [12], the high pressure solid phases of oxygen have been extensively investigated using structural [13][14][15], optical [7,8] and transport techniques [9]. A metallic state and evidence for superconductivity have been identified in the solid around 1M bar at very low temperatures [8,9]. The properties of the liquid on the other hand have not been explored much, due to experimental difficulties and also technical and conceptual challenges for theory.New insights on the physics of warm dense matter were provided by dynamic compression experiments on hydrogen [5,6]. We present the first electrical conductivity measurements of fluid oxygen under dynamic quasiisentropic compression between 0.3 and 1.9M bar. In our experiments fluid oxygen reaches up to 4-fold compression and temperatures below 7000K, conditions never before reached experimentally. We note that these conditions are similar with the ones found in the interiors of the giant planets, where oxygen is a major constituent, and that these conductivity measurements may be instrumental in explaining the origins of the planetary magnetic fields.We measured the electrical resistance of quasiisentropically compressed oxygen starting from high purity (99.995%), disk shaped liquid samples [16] of density d 0 = 1.202g/cm 3 at T 0 = 77K and atmospheric pressure. The hig...

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New High-Pressure Structural Transition of Oxygen at 96 GPa Associated with Metallization in a Molecular Solid

Cited by 180 publications

References 21 publications

Inelastic x-ray scattering of dense solid oxygen: Evidence for intermolecular bonding

Inelastic x-ray scattering of dense solid oxygen: Evidence for intermolecular bonding

X-ray crystallography of simple molecular solids up to megabar pressures: application to solid oxygen and carbon dioxide

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

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