Polymorphism in Amorphous Si<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Grimsditch, M.

doi:10.1103/physrevlett.52.2379

Cited by 336 publications

(182 citation statements)

References 20 publications

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“…Particular attention has been paid to silica because of its technological and geological importance. Polyamorphism is indeed observed in compression experiments on amorphous silica [37,38,39], and is also qualitatively reproduced in computer simulations [40,41,42]. Though not as dramatic as is found for amorphous solid water, the polyamorphism of silica may also be due to a trend toward liquid-liquid phase separation [43,44].…”

Section: Introductionmentioning

confidence: 57%

Computer simulations of liquid silica: Equation of state and liquid–liquid phase transition

Saika‐Voivod¹,

Sciortino²,

Poole³

2000

Phys. Rev. E

243

231

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We conduct extensive molecular dynamics computer simulations of two models for liquid silica [the model of Woodcock, Angell and Cheeseman, J. Phys. Chem. 65, 1565Chem. 65, (1976; and that of van Beest, Kramer and van Santen, Phys. Rev. Lett. 64, 1955, (1990)] to determine their thermodynamic properties at low temperature T across a wide density range. We find for both models a wide range of states in which isochores of the potential energy U are a linear function of T 3/5 , as recently proposed for simple liquids [Rosenfeld and P. Tarazona, Mol. Phys. 95, 141 (1998)]. We exploit this behavior to fit an accurate equation of state to our thermodynamic data. Extrapolation of this equation of state to low T predicts the occurrence of a liquid-liquid phase transition for both models. We conduct simulations in the region of the predicted phase transition, and confirm its existence by direct observation of phase separating droplets of atoms with distinct local density and coordination environments.

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Section: Introductionmentioning

confidence: 57%

Computer simulations of liquid silica: Equation of state and liquid–liquid phase transition

Saika‐Voivod¹,

Sciortino²,

Poole³

2000

Phys. Rev. E

243

231

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“…multiple structures of amorphous materials with the same composition separated by a first order phase transition) remains a fundamentally important and unresolved phenomenon [408]. A wealth of indirect evidence for such transitions has already been established in H2O [407], SiO2 [200,409,410], GeO2 [61,224,411], Si [198,412,413], I [414], Se [414,415], S [415,416], P [197,417], Ce [406]. However, unambiguous evidence for liquid-liquid transition has yet to be presented in the liquid state for any system.…”

Section: Non-crystalline Materialsmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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Pressure profoundly alters all states of matter. The symbiotic development of ultrahighpressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

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“…However, they also mentioned that the silica glass matrix undergoes structural and density changes within this pressure range, 22,23 so that it is not yet known if the structural changes are intrinsic to nanocrystalline ␤-Ga 2 O 3 , or are promoted by anomalous densification among the silica matrix. These results encourage us to reexamine the high-pressure behavior of freestanding ␤-Ga 2 O 3 nanoparticles by angle-dispersive x-ray diffraction ͑XRD͒ technique.…”

Section: Introductionmentioning

confidence: 99%

High-pressure behavior of β-Ga2O3 nanocrystals

Wang

Chen

et al. 2010

Journal of Applied Physics

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Freestanding nanocrystalline ␤-Ga 2 O 3 particles with an average grain size of 14 nm prepared by chemical method was investigated by angle-dispersive synchrotron x-ray diffraction in diamond-anvil cell up to 64.9 GPa at ambient temperature. The evolution of x-ray diffraction patterns indicated that nanocrystalline monoclinic ␤-Ga 2 O 3 underwent a phase transition to rhombohedral ␣-Ga 2 O 3 . It was found that ␤-to ␣-Ga 2 O 3 transition began at about 13.6-16.4 GPa, and extended up to 39.2 GPa. At the highest pressure used, only ␣-Ga 2 O 3 was present, which remained after pressure release. A Birch-Murnaghan fit to the P-V data yielded a zero-pressure bulk modulus at fixed B 0 Ј=4: B 0 = 228͑9͒ GPa and B 0 = 333͑19͒ GPa for ␤-Ga 2 O 3 and ␣-Ga 2 O 3 phases, respectively. We compared our results with bulk ␤-Ga 2 O 3 , and concluded that the phase-transition pressure and bulk modulus of nanocrystalline ␤-Ga 2 O 3 are higher than those of bulk counterpart.

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Polymorphism in Amorphous SiO2

Cited by 336 publications

References 20 publications

Computer simulations of liquid silica: Equation of state and liquid–liquid phase transition

Computer simulations of liquid silica: Equation of state and liquid–liquid phase transition

High-pressure studies with x-rays using diamond anvil cells

High-pressure behavior of β-Ga2O3 nanocrystals

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