Large-volume diamond cells for neutron diffraction above 90 GPa

Boehler, R.; Guthrie, Malcolm; Molaison, Jamie J.; Santos, A. M. dos; Sinogeikin, Stanislav V.; Machida, Shuichi; Pradhan, N.; Tulk, C. A.

doi:10.1080/08957959.2013.823197

Cited by 73 publications

(46 citation statements)

References 13 publications

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“…Below 37.9 GPa, our structural data are similar to those obtained around [15][16][17][18] GPa in previous studies (1,3,5). Because the first and second peak positions of G(r) in GeO 2 glass are considered to represent Ge-O and Ge-Ge distances, respectively, we compare the first and second peak positions of G(r) obtained in this study with Ge-O and Ge-Ge bond distances of crystalline GeO 2 with sixfold-coordinated CaCl 2 -type structure (21) (Fig.…”

Section: Significancesupporting

confidence: 77%

“…In such measurements, a large diffraction angle is essential for accurately determining the structure factor with sufficiently large coverage of momentum transfer Q (Q = 4πEsinθ/12.398, where E is X-ray energy in keV and θ is the diffraction angle), and for high resolution in the reduced pair distribution function in real space. Recently, generation of pressure up to 94 GPa has been achieved in a DAC with 1-mm culet size anvils (15). However, this large-volume DAC is designed for neutron diffraction measurement; it is difficult to apply this apparatus for X-ray diffraction measurement because of limited solid-angle access.…”

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confidence: 99%

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Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6

Kono

Kenney‐Benson

Ikuta

et al. 2016

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

107

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Knowledge of pressure-induced structural changes in glasses is important in various scientific fields as well as in engineering and industry. However, polyamorphism in glasses under high pressure remains poorly understood because of experimental challenges. Here we report new experimental findings of ultrahigh-pressure polyamorphism in GeO 2 glass, investigated using a newly developed double-stage large-volume cell. The Ge-O coordination number (CN) is found to remain constant at ∼6 between 22.6 and 37.9 GPa. At higher pressures, CN begins to increase rapidly and reaches 7.4 at 91.7 GPa. This transformation begins when the oxygen-packing fraction in GeO 2 glass is close to the maximal dense-packing state (the Kepler conjecture = ∼0.74), which provides new insights into structural changes in network-forming glasses and liquids with CN higher than 6 at ultrahigh-pressure conditions. high pressure | polyamorphism | glass | oxygen packing U nderstanding the structural response of network-forming glasses to pressure is of great interest not only in condensed matter physics, geoscience, and materials science, but also in engineering and industry. As prototype network-forming glasses, silica (SiO 2 ) and germania (GeO 2 ) have been the most extensively studied (1-5). These two glasses have similar structural change pathways at high pressures. At ambient pressure, both glasses are composed of corner-linked AO 4 tetrahedra, with atom A (Si or Ge) in fourfold coordination (6). Under compression, the coordination gradually changes from 4 to 6 over a wide pressure range [∼15-40 GPa for SiO 2 glass (2, 4) and ∼5-15 GPa for GeO 2 glass (1, 3, 5)].A recent study (7) found that evolution of network-forming structural motifs in glasses and liquids at high pressures can be rationalized in terms of oxygen-packing fraction (OPF). Fourfoldcoordinated structural motifs in SiO 2 and GeO 2 glasses are stable over a wide range of OPF between 0.40 and ∼0.59. The fourfoldcoordinated structural motifs become unstable when the OPF approaches the limit of random loose packing of hard spheres (0.55-0.60) (8, 9). When OPF >∼0.60, coordination number (CN) gradually increases with OPF to the limit of random close packing (0.64) (8, 9), where CN increases sharply to 6 with almost-constant OPF ∼0.64. Higher-pressure data for SiO 2 glass suggest the existence of another stability plateau for sixfold-coordinated structural motifs, with OPF of up to ∼0.72 (7).The highest coordination that has been experimentally determined so far in SiO 2 and GeO 2 glasses is 6. X-ray diffraction measurement for SiO 2 glass confirmed that sixfold-coordination structural motifs are stable up to 100 GPa (4). For GeO 2 glass, X-ray and neutron diffraction data are limited to 18 GPa (1, 3, 5). X-ray absorption spectroscopic measurements were conducted to 64 GPa (10, 11). Ref. 11 showed no major change in X-ray absorption fine structure up to 64 GPa, although a slight discontinuous change in density is observed around 40-45 GPa.Some simulation studies predicted the existe...

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Section: Significancesupporting

confidence: 77%

mentioning

confidence: 99%

Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6

Kono

Kenney‐Benson

Ikuta

et al. 2016

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

107

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“…Recent advances in DAC design can allow for relatively large sample sizes for a given pressure compared to conventional DACs. 15 Because we are interested in the inelastic scattering energy-loss spectra, and not diffuse elastic scattering, to a certain extent, a choice can be made of the gasket material. It may be possible to select a gasket material whose inelastic spectrum has features at given (q, ω) that is separated from that of the sample of interest.…”

Section: Minimizing Parasitic Scatteringmentioning

confidence: 99%

Focusing polycapillary to reduce parasitic scattering for inelastic x-ray measurements at high pressure

Chow

Xiao

Rod

et al. 2015

Review of Scientific Instruments

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The double-differential scattering cross-section for the inelastic scattering of x-ray photons from electrons is typically orders of magnitude smaller than that of elastic scattering. With samples 10-100 μm size in a diamond anvil cell at high pressure, the inelastic x-ray scattering signals from samples are obscured by scattering from the cell gasket and diamonds. One major experimental challenge is to measure a clean inelastic signal from the sample in a diamond anvil cell. Among the many strategies for doing this, we have used a focusing polycapillary as a post-sample optic, which allows essentially only scattered photons within its input field of view to be refocused and transmitted to the backscattering energy analyzer of the spectrometer. We describe the modified inelastic x-ray spectrometer and its alignment. With a focused incident beam which matches the sample size and the field of view of polycapillary, at relatively large scattering angles, the polycapillary effectively reduces parasitic scattering from the diamond anvil cell gasket and diamonds. Raw data collected from the helium exciton measured by x-ray inelastic scattering at high pressure using the polycapillary method are compared with those using conventional post-sample slit collimation.

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“…14). This design is very typical of the popular 'Dubna' cells, using BeCu to build the main cell body due to its high tensile strength and non-magnetic properties [155], and incorporating bevelled washer springs to try and keep the pressure application even over the anvils upon cooling of the cell. This cell, its dimensions limited so as to be incorporated into a cryostat, does not use the membrane design, meaning that the pressure cannot be varied at low temperature.…”

Section: Thin-walled Gas Cellmentioning

confidence: 99%

High pressure neutron and X-ray diffraction at low temperatures

Ridley

Kamenev

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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This paper presents a review of techniques and considerations in the design and construction of high pressure, low temperature diffraction experiments. Also intended as an introductory text to new high pressure users, the crucial aspects of pressure cell design are covered. The general classification of common designs, and a discussion into the key beam interaction, mechanical, and thermal properties of commonly used materials is given. The advantages of different materials and high pressure cell classifications are discussed, and examples of designs developed for low temperature diffraction studies are presented, and compared.

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Large-volume diamond cells for neutron diffraction above 90 GPa

Cited by 73 publications

References 13 publications

Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6

Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6

Focusing polycapillary to reduce parasitic scattering for inelastic x-ray measurements at high pressure

High pressure neutron and X-ray diffraction at low temperatures

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Large-volume diamond cells for neutron diffraction above 90 GPa

Cited by 73 publications

References 13 publications

Ultrahigh-pressure polyamorphism in GeO 2 glass with coordination number >6

Ultrahigh-pressure polyamorphism in GeO 2 glass with coordination number >6

Focusing polycapillary to reduce parasitic scattering for inelastic x-ray measurements at high pressure

High pressure neutron and X-ray diffraction at low temperatures

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Product

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Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6

Ultrahigh-pressure polyamorphism in GeO ₂ glass with coordination number >6