In situ structural changes of amorphous diopside (CaMgSi2O6) up to 20 GPa: A Raman and O K-edge X-ray Raman spectroscopic study

Moulton, Benjamin J.A.; Henderson, Grant S.; Fukui, Hiroshi; Hiraoka, Nozomu; Ligny, Dominique de; Sonneville, Camille; Kanzaki, Masami

doi:10.1016/j.gca.2016.01.020

Cited by 28 publications

(14 citation statements)

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“…) as well as other more complex glasses up to ∼40 GPa has been reported (25,29,(34)(35)(36). Furthermore, a silicon L-edge spectrum was obtained for v-SiO 2 up to ∼74 GPa (37).…”

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confidence: 54%

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

Lee

Kim

Chow

et al. 2018

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

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Structural transition in amorphous oxides, including glasses, under extreme compression above megabar pressures (>1 million atmospheric pressure, 100 GPa) results in unique densification paths that differ from those in crystals. Experimentally verifying the atomistic origins of such densifications beyond 100 GPa remains unknown. Progress in inelastic X-ray scattering (IXS) provided insights into the pressure-induced bonding changes in oxide glasses; however, IXS has a signal intensity several orders of magnitude smaller than that of elastic X-rays, posing challenges for probing glass structures above 100 GPa near the Earth's core-mantle boundary. Here, we report megabar IXS spectra for prototypical BO glasses at high pressure up to ∼120 GPa, where it is found that only four-coordinated boron (B) is prevalent. The reduction in the B-O length up to 120 GPa is minor, indicating the extended stability of-bonded B. In contrast, a substantial decrease in the average O-O distance upon compression is revealed, suggesting that the densification in BO glasses is primarily due to O-O distance reduction without the formation of B. Together with earlier results with other archetypal oxide glasses, such as SiO and GeO, the current results confirm that the transition pressure of the formation of highly coordinated framework cations systematically increases with the decreasing atomic radius of the cations. These observations highlight a new opportunity to study the structure of oxide glass above megabar pressures, yielding the atomistic origins of densification in melts at the Earth's core-mantle boundary.

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“…) as well as other more complex glasses up to ∼40 GPa has been reported (25,29,(34)(35)(36). Furthermore, a silicon L-edge spectrum was obtained for v-SiO 2 up to ∼74 GPa (37).…”

mentioning

confidence: 54%

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

Lee

Kim

Chow

et al. 2018

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

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“…The effect of pressure in short-range order structure of germanates-based oxide glasses as, GeO 2 , Li 2 O-4GeO 2 , SiO 2 -GeO 2 and La 2 O 3 -B 2 O 3 -GeO 2 glass systems have been studied by different authors [ 128 , 129 , 130 , 131 , 132 , 133 , 134 ]. Recently, Mouton et al studied the high-pressure structural changes in diopside glass by analyzing oxygen K-edge XANES data and revealed that diopside shows a clear structural transition around 4 GPa and a probable second transition between 12 and 14 GPa [ 135 ]. We also found in the literature pressure-induced structural changes where the XANES spectra of K 2 TiSi 4 O 11 silicate glass was collected from the samples quenched from different pressures [ 58 ].…”

Section: Examples Of Using the Xafs Technique To Study The Atomic mentioning

confidence: 99%

X-ray Absorption Fine Structure (XAFS) Studies of Oxide Glasses—A 45-Year Overview

Mastelaro

Zanotto

2018

Materials

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X-ray Absorption Fine Structure (XAFS) spectroscopy has been widely used to characterize the short-range order of glassy materials since the theoretical basis was established 45 years ago. Soon after the technique became accessible, mainly due to the existence of Synchrotron laboratories, a wide range of glassy materials was characterized. Silicate glasses have been the most studied because they are easy to prepare, they have commercial value and are similar to natural glasses, but borate, germanate, phosphate, tellurite and other less frequent oxide glasses have also been studied. In this manuscript, we review reported advances in the structural characterization of oxide-based glasses using this technique. A focus is on structural characterization of transition metal ions, especially Ti, Fe, and Ni, and their role in different properties of synthetic oxide-based glasses, as well as their important function in the formation of natural glasses and magmas, and in nucleation and crystallization. We also give some examples of XAFS applications for structural characterization of glasses submitted to high pressure, glasses used to store radioactive waste and medieval glasses. This updated, comprehensive review will likely serve as a useful guide to clarify the details of the short-range structure of oxide glasses.

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“…In MgSiO 3 melt at 1 atm, polyhedral units (i.e., Si coordinated by multiple oxygen atoms in the first coordination shell, [4] Si) are bridged through the [2] O (bridging oxygen; BO) and nonbridging oxygen [1] O (NBO) (Allwardt & Stebbins, ; Gaudio et al, ; Lee et al, , ). Below ~50 GPa, the structures of MgSiO 3 glasses have been extensively explored, revealing a decrease in the Si‐O‐Si angle and an increase in the Mg and Si coordination numbers upon compression (e.g., Fukui & Hiraoka, ; Kubicki et al, ; Lee et al, ; Moulton et al, ; Salmon et al, ; Wang et al, , and references therein). Pioneering X‐ray and Brillouin scattering studies of MgSiO 3 glasses above megabar pressure conditions (Kono et al, ; Murakami & Bass, ) revealed pressure‐induced changes in the structure factors and acoustic wave velocities at ~90–140 GPa, suggesting the emergence of highly coordinated Si.…”

Section: Introductionmentioning

confidence: 99%

Structural Transitions in MgSiO₃ Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering

Kim

et al. 2019

Geophysical Research Letters

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The structural adaptation in MgSiO 3 melts under compression up to 130 GPa is the key to revealing the origins of the pronounced negative buoyancy of the melts at the core-mantle boundary (CMB). A full understanding of the melt densification requires study of the pressure-induced changes in the bonding configuration around oxygen at the CMB, which has proven to be difficult to measure. Here, the experimental breakthrough in O K-edge inelastic X-ray scattering enables collection of the spectra of MgSiO 3 glasses up to~130 GPa, along with ab initio molecular dynamics simulations, revealing the electronic bonding transitions around heavily compressed oxygen. The spectral results indicate the emergence of denser network structures around oxygen, stemming from contractions in the Mg-O and O-O distances associated with flexible topological and short-range rearrangements around Si. The results unveil the electronic structure and thus the nature of densification in dense partial melts at the CMB.Plain Language Summary A thin ultralow velocity zone at the bottom of mantle is characterized by reduced seismic wave velocities and enhanced density, suggesting the possible presence of molten silicates at a depth of~2,850 km (~130 GPa of pressure). How the melts densify near the core-mantle boundary is unclear. Because oxygen occupies the major volume fraction of silicates, the melt densification is dominated by the reorganization of oxygen during compression. However, the oxygen bonding environments in MgSiO 3 melt-a model mantle melt-near the core-mantle boundary are unknown. Here, the inelastic X-ray scattering spectra of MgSiO 3 glasses and liquids up to~130 GPa revealed the electronic bonding transitions around compressed oxygen that are not observed at low pressures and substantially differ from those in the crystalline MgSiO 3 bridgmanite. The spectral results indicate the pressure-induced emergence of denser network structures around oxygen, stemming from gradual contractions in the Mg-O and O-O distances associated with flexible topological and short-range rearrangements around Si. The densification around oxygen near megabar pressures potentially contributes to the gravitational stabilization of the complex partial melts in the deeper part of the mantle toward ultralow velocity zone.

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In situ structural changes of amorphous diopside (CaMgSi2O6) up to 20 GPa: A Raman and O K-edge X-ray Raman spectroscopic study

Cited by 28 publications

References 104 publications

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

X-ray Absorption Fine Structure (XAFS) Studies of Oxide Glasses—A 45-Year Overview

Structural Transitions in MgSiO₃ Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering

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In situ structural changes of amorphous diopside (CaMgSi2O6) up to 20 GPa: A Raman and O K-edge X-ray Raman spectroscopic study

Cited by 28 publications

References 104 publications

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

Amorphous boron oxide at megabar pressures via inelastic X-ray scattering

X-ray Absorption Fine Structure (XAFS) Studies of Oxide Glasses—A 45-Year Overview

Structural Transitions in MgSiO3 Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering

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Structural Transitions in MgSiO₃ Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering