scholarly journals Structural Transitions in MgSiO 3 Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering

2019 ◽  
Vol 46 (23) ◽  
pp. 13756-13764 ◽  
Author(s):  
Yong‐Hyun Kim ◽  
Yoo Soo Yi ◽  
Hyo‐Im Kim ◽  
Paul Chow ◽  
Yuming Xiao ◽  
...  
Keyword(s):  
Structural Transitions ◽  
X Ray ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
X Ray Scattering ◽  
Ray Scattering

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

2018 ◽  
Vol 115 (23) ◽  
pp. 5855-5860 ◽  
Author(s):  
Sung Keun Lee ◽  
Yong-Hyun Kim ◽  
Paul Chow ◽  
Yunming Xiao ◽  
Cheng Ji ◽  
...  
Keyword(s):  
Oxide Glass ◽  
X Rays ◽  
Oxide Glasses ◽  
Earth’S Core ◽  
Earth's Core ◽  
X Ray ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
X Ray Scattering ◽  
Ray Scattering

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 B2O3 glasses at high pressure up to ∼120 GPa, where it is found that only four-coordinated boron ([4]B) is prevalent. The reduction in the [4]B–O length up to 120 GPa is minor, indicating the extended stability of sp3-bonded [4]B. In contrast, a substantial decrease in the average O–O distance upon compression is revealed, suggesting that the densification in B2O3 glasses is primarily due to O–O distance reduction without the formation of [5]B. Together with earlier results with other archetypal oxide glasses, such as SiO2 and GeO2, 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.

scholarly journals Spectral weight of resonant inelastic X-ray scattering in doped cuprates: Effect of core-hole lifetime

2018 ◽  
Vol 32 (17) ◽  
pp. 1840017 ◽  
Author(s):  
Takami Tohyama ◽  
Kenji Tsutsui
Keyword(s):  
Spectral Weight ◽  
Main Peak ◽  
Core Hole ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Spin Flip ◽  
X Ray Absorption ◽  
Magnon Excitation ◽  
Ray Scattering

We examine the effect of core-hole lifetime on the spectral weight of resonant inelastic X-ray scattering (RIXS) in hole-doped cuprates. We calculate the spectral weight by using the exact diagonalization technique for a 4 × 4 doped Hubbard lattice and find that the spin-flip channel detecting single-magnon excitation is less sensitive to the core-hole lifetime while in the non-spin-flip channel the spectral weight is strongly dependent on the lifetime. In the latter, charge and two-magnon excitations predominately contribute to RIXS for short and long core-hole lifetimes, respectively. For a realistic value of the core-hole lifetime in cuprates, both the charge and two-magnon excitations are expected to contribute to the non-spin-flip channel in RIXS when the incident-photon energy is tuned to the main peak of X-ray absorption spectrum.

scholarly journals Direct monitoring of calcium-triggered phase transitions in cubosomes using small-angle X-ray scattering combined with microfluidics

2016 ◽  
Vol 49 (6) ◽  
pp. 2005-2014 ◽  
Author(s):  
Aghiad Ghazal ◽  
Mark Gontsarik ◽  
Jörg P. Kutter ◽  
Josiane P. Lafleur ◽  
Ana Labrador ◽  
...  
Keyword(s):  
Microfluidic Device ◽  
Small Angle ◽  
Soft Lithography ◽  
Time Frame ◽  
Cubic Phase ◽  
Structural Transitions ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

This article introduces a simple microfluidic device that can be combined with synchrotron small-angle X-ray scattering (SAXS) for monitoring dynamic structural transitions. The microfluidic device is a thiol–ene-based system equipped with 125 µm-thick polystyrene windows, which are suitable for X-ray experiments. The device was prepared by soft lithography using elastomeric molds followed by a simple UV-initiated curing step to polymerize the chip material and simultaneously seal the device with the polystyrene windows. The microfluidic device was successfully used to explore the dynamics of the structural transitions of phytantriol/dioleoylphosphatidylglycerol-based cubosomes on exposure to a buffer containing calcium ions. The resulting SAXS data were resolved in the time frame between 0.5 and 5.5 s, and a calcium-triggered structural transition from an internal inverted-type cubic phase of symmetryIm3mto an internal inverted-type cubic phase of symmetryPn3mwas detected. The combination of microfluidics with X-ray techniques opens the door to the investigation of early dynamic structural transitions, which is not possible with conventional techniques such as glass flow cells. The combination of microfluidics with X-ray techniques can be used for investigating protein unfolding, for monitoring the formation of nanoparticles in real time, and for other biomedical and pharmaceutical investigations.

scholarly journals Towards identifying the active sites on RuO2(110) in catalyzing oxygen evolution

2017 ◽  
Vol 10 (12) ◽  
pp. 2626-2637 ◽  
Author(s):  
Reshma R. Rao ◽  
Manuel J. Kolb ◽  
Niels Bendtsen Halck ◽  
Anders Filsøe Pedersen ◽  
Apurva Mehta ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Oxygen Evolution ◽  
Active Sites ◽  
Density Functional ◽  
Structural Transitions ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Surface structural transitions and active sites are identified using X-ray scattering and density functional theory.

Study of the internal structure of polymer micelles by anomalous small-angle X-ray scattering at two edges

2013 ◽  
Vol 46 (5) ◽  
pp. 1407-1413 ◽  
Author(s):  
Megumi Sakou ◽  
Atsuro Takechi ◽  
Shin-ichi Murakami ◽  
Kazuo Sakurai ◽  
Isamu Akiba
Keyword(s):  
Spatial Distribution ◽  
Form Factor ◽  
Small Angle ◽  
Form Factors ◽  
Solid Sphere ◽  
Hydrophobic Core ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Ray Scattering

Anomalous small-angle X-ray scattering with two marker elements was applied to the structural analysis of poly(4-vinylphenol rubidium salt)-block-poly(4-bromostyrene) (RbPVPh-b-PBrS) micelles, where Br and Rb were the markers for the hydrophobic core and the hydrated corona, respectively. By using two different markers for the hydrophobic core and the hydrated corona, the form factors of the core and corona were extracted separately from the scattering profile of the whole RbPVPh-b-PBrS micelles. The form factor of the hydrophobic core (the spatial distribution of Br) revealed that the core was regarded as a solid sphere with a smooth surface and a radius of 47 nm. Conversely, the form factor of the spatial distribution of Rb+indicated that the shell of the RbPVPh-b-PBrS micelles was 15 nm thick.

Nuclear dynamics in the core-excited state of aqueous ammonia probed by resonant inelastic soft x-ray scattering

2011 ◽  
Vol 84 (10) ◽  
Author(s):  
L. Weinhardt ◽  
M. Weigand ◽  
O. Fuchs ◽  
M. Bär ◽  
M. Blum ◽  
...  
Keyword(s):  
Excited State ◽  
Aqueous Ammonia ◽  
Nuclear Dynamics ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Electron dynamics in the core-excited CS2 molecule revealed through resonant inelastic x-ray scattering spectroscopy

2015 ◽  
Vol 635 (11) ◽  
pp. 112012
Author(s):  
T Marchenko ◽  
S Carniato ◽  
L Journel ◽  
R Guillemin ◽  
E Kawerk ◽  
...  
Keyword(s):  
Electron Dynamics ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Ray Scattering

Nanostructural analysis of GaN tripods and hexapods grown onc-plane sapphire

2010 ◽  
Vol 43 (6) ◽  
pp. 1300-1304 ◽  
Author(s):  
Sanghwa Lee ◽  
Yuri Sohn ◽  
Chinkyo Kim ◽  
Dong Ryeol Lee ◽  
Hyun-Hwi Lee
Keyword(s):  
Structural Characteristics ◽  
Microscopic Analysis ◽  
Crystallographic Analysis ◽  
Core Size ◽  
X Ray ◽  
The Core ◽  
Sapphire Substrates ◽  
X Ray Scattering ◽  
Inversion Domain ◽  
Ray Scattering

The crystallographic and structural characteristics of GaN tripods and hexapods grown onc-plane sapphire substrates were investigated using synchrotron X-ray scattering and microscopic analysis. The core structure of a GaN hexapod is revealed to be in the zincblende phase with an inversion domain, and a refined crystallographic analysis of tripods and hexapods with synchrotron X-ray scattering shows the existence of the zincblende phase in wurtzite-based protruding nanorods. The atomistic model combined with this crystallographic analysis reveals that the core size of a hexapod is much smaller than the diameters of the protruding nanorods. This refined structural analysis can be utilized in tailoring the opto-electronic characteristics of GaN multipods.

A one-term Gaussian representation of the x-ray scattering factor of core electrons

1971 ◽  
Vol 134 (1-2) ◽  
Author(s):  
C. J. De Ranter ◽  
M. Van Dijck
Keyword(s):  
Gaussian Function ◽  
Electron Shell ◽  
Simple Relation ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Gaussian Representation ◽  
Core Electrons ◽  
Scattering Factor ◽  
Ray Scattering

AbstractIn an attempt to treat independently the contribution of the inner and outer electrons of the different atoms to the total x-ray scattering the selected-electron shell (SES) method was developped, representing the atomic scattering factor by a three- or four-term Gaussian polynomial and associating the Gaussian constants with the electron shells of the atom.For most atoms however and contrary to the hypothesis no simple relation can be made.Therefore, the atom is considered as a non-rigid body, built up from two distinguishable terms: the core and the outer electrons. The core is assumed to form a closed, spherically symmetric shell, making an overall description of its scattering power by a one-term Gaussian function, within some limits in reciprocal space, quite possible. The

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