TY  - JOUR
A1  - Cerantola, Valerio
A1  - Wilke, Max
A1  - Kantor, Innokenty
A1  - Ismailova, Leyla
A1  - Kupenko, Ilya
A1  - McCammon, Catherine
A1  - Pascarelli, Sakura
A1  - Dubrovinsky, Leonid S.
T1  - Experimental investigation of FeCO3 (siderite) stability in Earth's lower mantle using XANES spectroscopy
JF  - American mineralogist : an international journal of earth and planetary materials
N2  - We studied FeCO3 using Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy at pressures up to 54 GPa and temperatures above 2000 K. First-principles calculations of Fe at the K-edge in FeCO3 were performed to support the interpretation of the XANES spectra. The variation of iron absorption edge features with pressure and temperature in FeCO3 matches well with recently reported observations on FeCO3 at extreme conditions, and provides new insight into the stability of Fe-carbonates in Earth's mantle. Here we show that at conditions of the mid-lower mantle, ~50 GPa and ~2200 K, FeCO3 melts and partially decomposes to high-pressure Fe3O4. Carbon (diamond) and oxygen are also inferred products of the reaction. We constrained the thermodynamic phase boundary between crystalline FeCO3 and melt to be at 51(1) GPa and ~1850 K. We observe that at 54(1) GPa, temperature-induced spin crossover of Fe2+ takes place from low to high spin such that at 1735(100) K, all iron in FeCO3 is in the high-spin state. A comparison between experiment and theory provides a more detailed understanding of FeCO3 decomposition observed in X-ray absorption spectra and helps to explain spectral changes due to pressure-induced spin crossover in FeCO3 at ambient temperature.
KW  - Deep carbon cycle
KW  - siderite
KW  - decomposition
KW  - melting
KW  - spin transition
KW  - Earth in Five Reactions: A Deep Carbon Perspective
Y1  - 2019
U6  - https://doi.org/10.2138/am-2019-6428
SN  - 0003-004X
SN  - 1945-3027
VL  - 104
IS  - 8
SP  - 1083
EP  - 1091
PB  - Mineralogical Society of America
CY  - Chantilly
ER  - 
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  - Weis, Christopher
A1  - Sternemann, Christian
A1  - Cerantola, Valerio
A1  - Sahle, Christoph J.
A1  - Spiekermann, Georg
A1  - Harder, Manuel
A1  - Forov, Yury
A1  - Kononov, Alexander
A1  - Sakrowski, Robin
A1  - Yavas, Hasan
A1  - Tolan, Metin
A1  - Wilke, Max
T1  - Pressure driven spin transition in siderite and magnesiosiderite single crystals
JF  - Scientific reports
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-16733-3
SN  - 2045-2322
VL  - 7
PB  - Nature Publ. Group
CY  - London
ER  -