TY  - JOUR
A1  - Schifferle, Lukas
A1  - Lobanov, Sergey S.
T1  - Evolution of chemical bonding and spin-pairing energy in ferropericlase across Its spin transition
JF  - ACS Earth and Space Chemistry
N2  - The evolution of chemical bonding in ferropericlase, (Mg,Fe)O, with pressure may affect the physical and chemical properties of the Earth's lower mantle. Here, we report high-pressure optical absorption spectra of single-crystalline ferropericlase ((Mg0.87Fe0.13)O) up to 135 GPa. Combined with a re-evaluation of published partial fluorescence yield X-ray absorption spectroscopy data, we show that the covalency of the Fe-O bond increases with pressure, but the iron spin transition at 57-76.5 GPa reverses this trend. The qualitative crossover in chemical bonding suggests that the spin-pairing transition weakens the Fe-O bond in ferropericlase. We find, that the spin transition in ferropericlase is caused by both the increase of the ligand field-splitting energy and the decrease in the spin-pairing energy of high-spin Fe2+.
KW  - high-pressure
KW  - diamond anvil cell
KW  - covalency
KW  - bond strength
KW  - iron
KW  - spin
KW  - transition
Y1  - 2022
U6  - https://doi.org/10.1021/acsearthspacechem.2c00014
SN  - 2472-3452
VL  - 6
IS  - 3
SP  - 788
EP  - 799
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sternemann, C.
A1  - Wilke, Max
T1  - Spectroscopy of low and intermediate Z elements at extreme conditions: in situ studies of Earth materials at pressure and temperature via X-ray Raman scattering
JF  - High pressure research
N2  - X-ray Raman scattering spectroscopy is an emerging method in the study of low and intermediate Z elements' core-electron excitations at extreme conditions in order to reveal information on local structure and electronic state of matter in situ. We discuss the capabilities of this method to address questions in Earth materials' science and demonstrate its sensitivity to detect changes in the oxidation state, electronic structure, coordination, and spin state. Examples are presented for the study of the oxygen K-, silicon L- and iron M-edges. We assess the application of both temperature and pressure in such investigations exploiting diamond anvil cells in combination with resistive or laser heating which is required to achieve realistic conditions of the Earth's crust, mantle, and core.
KW  - X-ray Raman scattering
KW  - inelastic X-ray scattering
KW  - X-ray absorption
KW  - high pressure research
KW  - diamond anvil cell
KW  - minerals
KW  - glasses
KW  - melts
KW  - Earth materials
KW  - spin transition
KW  - bonding transition
KW  - coordination transformation
KW  - oxidation state
KW  - electronic structure
Y1  - 2016
U6  - https://doi.org/10.1080/08957959.2016.1198903
SN  - 0895-7959
SN  - 1477-2299
VL  - 36
SP  - 275
EP  - 292
PB  - IOP Publ. Ltd.
CY  - Abingdon
ER  -