TY  - JOUR
A1  - Weis, Christopher
A1  - Spiekermann, Georg
A1  - Sternemann, Christian
A1  - Harder, Manuel
A1  - Vanko, Gyorgy
A1  - Cerantola, Valerio
A1  - Sahle, Christoph J.
A1  - Forov, Yury
A1  - Sakrowski, Robin
A1  - Kupenko, Ilya
A1  - Petitgirard, Sylvain
A1  - Yavas, Hasan
A1  - Bressler, Christian
A1  - Gawelda, Wojciech
A1  - Tolan, Metin
A1  - Wilke, Max
T1  - Combining X-ray K beta(1,3), valence-to-core, and X-ray Raman spectroscopy for studying Earth materials at high pressure and temperature
BT  - the case of siderite
JF  - Journal of analytical atomic spectrometry
N2  - X-ray emission and X-ray Raman scattering spectroscopy are powerful tools to investigate the local electronic and atomic structure of high and low Z elements in situ. Notably, these methods can be applied for in situ spectroscopy at high pressure and high temperature using resistively or laser-heated diamond anvil cells in order to achieve thermodynamic conditions which appear in the Earth's interior. We present a setup for combined X-ray emission and X-ray Raman scattering studies at beamline P01 of PETRA III using a portable wavelength-dispersive von Hamos spectrometer together with the permanently installed multiple-analyzer Johann-type spectrometer. The capabilities of this setup are exemplified by investigating the iron spin crossover of siderite FeCO3 up to 49.3 GPa by measuring the Fe M2,3-edge and the Fe Kβ1,3 emission line simultaneously. With this setup, the Fe valence-to-core emission can be detected together with the Kβ1,3 emission line providing complementary information on the sample's electronic structure. By implementing a laser-heating device, we demonstrate the strength of using a von Hamos type spectrometer for spin state mapping at extreme conditions. Finally, we give different examples of low Z elements' absorption edges relevant for application in geoscience that are accessible with the Johann-type XRS spectrometer. With this setup new insights into the spin transition and compression mechanisms of Earth's mantle materials can be obtained of importance for comprehension of the macroscopic physical and chemical properties of the Earth's interior.
Y1  - 2018
U6  - https://doi.org/10.1039/c8ja00247a
SN  - 0267-9477
SN  - 1364-5544
VL  - 34
IS  - 2
SP  - 384
EP  - 393
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Petitgirard, Sylvain
A1  - Spiekermann, Georg
A1  - Glazyrin, Konstantin
A1  - Garrevoet, Jan
A1  - Murakami, Motohiko
T1  - Density of amorphous GeO2 to 133 GPa with possible pyritelike structure and stiffness at high pressure
JF  - Physical review : B, Condensed matter and materials physics
N2  - Germanium oxide is a prototype network-forming oxide with pressure-induced structural changes similar to those found in crystals and amorphous silicate oxides at high pressure. Studying density and coordination changes in amorphous GeO2 allows for insight into structural changes in silicate oxides at very high pressure, with implications for the properties of planetary magmas. Here, we report the density of germanium oxide glass up to 133 GPa using the x-ray absorption technique, with very good agreement with previous experimental data at pressure below 40 GPa and recent calculation up to 140 GPa. Our data highlight four distinct compressibility domains, corresponding to changes of the local structure of GeO2. Above 80 GPa, our density data show a compressibility and bulk modulus similar to the counterpart crystal phase, and we propose that a compact distorted sixfold coordination, similar to the structural motif of the pyritelike crystalline GeO2 polymorph, is likely to be stable in that pressure range. Our density data point to a smooth continuous evolution of the average coordination for pressure above 20 GPa with persistent sixfold coordination, without sharp density or density slope discontinuities. These observations are in very good agreement with theoretical calculations and spectroscopic measurements, and our results indicate that glasses and melts may behave similarly to their high-pressure solid counterparts with comparable densities, compressibility, and possibly average coordination.
Y1  - 2019
U6  - https://doi.org/10.1103/PhysRevB.100.214104
SN  - 2469-9950
SN  - 2469-9969
VL  - 100
IS  - 21
PB  - American Physical Society
CY  - College Park
ER  -