Oxygen phase equilibria near 298 K

Nicol, Malcolm; Hirsch, K.; Holzapfel, W. B.

doi:10.1016/0009-2614(79)80066-4

Cited by 101 publications

(46 citation statements)

References 6 publications

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“…The sample was placed on an automated Picker diffractometer and the unit cell was shown to be face-centered orthorhom- * The most common description of this color was orange, but observers taking turns at the microscope described the same sample variously as orange, pink, magenta, purple and yellow! The absorption spectrum is similar to that reported by Nicol et al (1979) and shows a rather broad (ca 100 nm FWHM) peak centered at about 510 nm and skewed toward the short-wavelength region. The extreme variation in the color perceived probably results from different relative sensitivities of the eyes of various observers to different parts of the spectrum.…”

Section: Methodssupporting

confidence: 83%

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

Schiferl¹,

Cromer²,

Schwalbe³

et al. 1983

Acta Crystallogr Sect B

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A single crystal of 'orange' 1802 at 9.6 (3) GPa and 297 (1) K was produced in a Merrill-Bassett diamondanvil high-pressure cell and examined by X-ray diffraction. Pressure was determined with the rubyfluorescence method. The unit cell is orthorhombic, space group Fmmm, lattice constants a = 4.2151 (6), b = 2.9567 (4), c = 6.6897 (17)A, molar volume = 12.56 x 10 -6 m 3 mol -~ with four molecules per unit cell. The charge densities of the molecules overlap or distort to a considerable degree. Generalized scattering factors were used in an aspherical-atom least-squares * Work performed under the auspices of the US Department of Energy.0567-7408/83/020153-05501.50 refinement. For five refined parameters and 24 observations the final R w is 0.056. A correction is made to our previous work on fl-O2 at 5.5 GPa and 299 K.

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Section: Methodssupporting

confidence: 83%

“…1802 was used instead of normal oxygen gas, which is almost entirely 160 2 , in the hope that the transition pressures would be lowered a few kilobars by the mass-isotope effect. This was an important consideration because the transitions reported by Nicol et al (1979) occur barely within the pressure capability of our Merrill-Bassett cells.…”

Section: Methodsmentioning

confidence: 99%

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

Schiferl¹,

Cromer²,

Schwalbe³

et al. 1983

Acta Crystallogr Sect B

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“…Fluid O 2 exists to 5.5 GPa and solidifies upon further compression, forming the rombohedral ␤-phase (1) at 5.5 GPa, the orthorhmbic ␦-phase (2) at 9.6 GPa, the monoclinic -phase (3, 4) at 10 GPa, and the modified monoclinic -phase (5) at 96 GPa. These transformations are accompanied by marked changes in color, density, and vibrational dynamics (6)(7)(8)(9), and by metallization (10), including the appearance of superconductivity at low temperatures (11). These remarkable phenomena in condensed oxygen are consequences of pressure-induced changes in electronic structure and bonding, an area of fundamental importance but previously inaccessible by in situ high-pressure studies.…”

mentioning

confidence: 99%

“…These remarkable phenomena in condensed oxygen are consequences of pressure-induced changes in electronic structure and bonding, an area of fundamental importance but previously inaccessible by in situ high-pressure studies. Raman and infrared observations of the -phase, specifically the anomaly in the intramolecular vibrational frequencies of O 2 (6,8) and the appearance of strong infrared absorption (7,8), have led to suggestions of increased intermolecular interaction, electronic charge transfer, and a paired O 2 model for the -phase. The tendency toward association of O 2 molecules in the -phase was also proposed based on results of early density functional calculations (12).…”

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confidence: 99%

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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“…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].…”

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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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Oxygen phase equilibria near 298 K

Cited by 101 publications

References 6 publications

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

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

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

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

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Oxygen phase equilibria near 298 K

Cited by 101 publications

References 6 publications

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

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

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

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

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About

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

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