TY  - JOUR
A1  - Petitgirard, Sylvian
A1  - Sahle, C. J.
A1  - Weis, C.
A1  - Gilmore, K.
A1  - Spiekermann, Georg
A1  - Tse, J. S.
A1  - Wilke, Max
A1  - Cavallari, C.
A1  - Cerantola, V
A1  - Sternemann, Christian
T1  - Magma properties at deep Earth’s conditions from electronic structure of silica
JF  - Geochemical perspectives letters
N2  - SiO(2 )is the main component of silicate melts and thus controls their network structure and physical properties. The compressibility and viscosities of melts at depth are governed by their short range atomic and electronic structure. We measured the O K-edge and the Si L-2,L-3-edge in silica up to 110 GPa using X-ray Raman scattering spectroscopy, and found a striking match to calculated spectra based on structures from molecular dynamic simulations. Between 20 and 27 GPa, Si-[4] species are converted into a mixture of Si-[5] and Si-[6] species and between 60 and 70 GPa, Si-[6] becomes dominant at the expense of Si-[5] with no further increase up to at least 110 GPa. Coordination higher than 6 is only reached beyond 140 GPa, corroborating results from Brillouin scattering. Network modifying elements in silicate melts may shift this change in coordination to lower pressures and thus magmas could be denser than residual solids at the depth of the core-mantle boundary.
Y1  - 2019
U6  - https://doi.org/10.7185/geochemlet.1902
SN  - 2410-339X
SN  - 2410-3403
VL  - 9
SP  - 32
EP  - 37
PB  - Association of Geochemistry
CY  - Paris
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  -