TY  - JOUR
A1  - Sahle, Christoph J.
A1  - Niskanen, Johannes
A1  - Schmidt, Christian
A1  - Stefanski, Johannes
A1  - Gilmore, Keith
A1  - Forov, Yury
A1  - Jahn, Sandro
A1  - Wilke, Max
A1  - Sternemann, Christian
T1  - Cation Hydration in Supercritical NaOH and HCl Aqueous Solutions
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - We present a study of the local atomic environment of the oxygen atoms in the aqueous solutions of NaOH and HCl under simultaneous high-temperature and high-pressure conditions. Experimental nonresonant X-ray Raman scattering core-level spectra at the oxygen K-edge show systematic changes as a function of temperature and pressure. These systematic changes are distinct for the two different solutes and are described well by calculations within the Bethe- Salpeter formalism for snapshots from ab initio molecular dynamics simulations. The agreement between experimental and simulation results allows us to use the computations for a detailed fingerprinting analysis in an effort to elucidate the local atomic structure and hydrogen-bonding topology in these relevant solutions. We observe that both electrolytes, especially NaOH, enhance hydrogen bonding and tetrahedrality in the water structure at supercritical conditions, in particular in the vicinity of the hydration shells. This effect is accompanied with the association of the HCl and NaOH molecules at elevated temperatures.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.jpcb.7b09688
SN  - 1520-6106
VL  - 121
SP  - 11383
EP  - 11389
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Spiekermann, Georg
A1  - Harder, M.
A1  - Gilmore, Keith
A1  - Zalden, Peter
A1  - Sahle, Christoph J.
A1  - Petitgirard, Sylvain
A1  - Wilke, Max
A1  - Biedermann, Nicole
A1  - Weis, Thomas
A1  - Morgenroth, Wolfgang
A1  - Tse, John S.
A1  - Kulik, E.
A1  - Nishiyama, Norimasa
A1  - Yavaş, Hasan
A1  - Sternemann, Christian
T1  - Persistent Octahedral Coordination in Amorphous GeO₂ Up to 100 GPa
by Kβ'' X-Ray Emission Spectroscopy
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - We measure valence-to-core x-ray emission spectra of compressed crystalline GeO₂ up to 56 GPa and of amorphous GeO₂ up to 100 GPa. In a novel approach, we extract the Ge coordination number and mean Ge-O distances from the emission energy and the intensity of the Kβ'' emission line. The spectra of high-pressure polymorphs are calculated using the Bethe-Salpeter equation. Trends observed in the experimental and calculated spectra are found to match only when utilizing an octahedral model. The results reveal persistent octahedral Ge coordination with increasing distortion, similar to the compaction mechanism in the sequence of octahedrally coordinated crystalline GeO₂ high-pressure polymorphs.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 699 
KW  - rutile-type
KW  - glass
KW  - crystalline
KW  - pressures
KW  - complexes
KW  - silicon
KW  - oxygen
KW  - SIO₂
KW  - MO
KW  - CU
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427755
SN  - 1866-8372
IS  - 699
ER  - 
TY  - JOUR
A1  - Spiekermann, Georg
A1  - Harder, M.
A1  - Gilmore, Keith
A1  - Zalden, Peter
A1  - Sahle, Christoph J.
A1  - Petitgirard, Sylvain
A1  - Wilke, Max
A1  - Biedermann, Nicole
A1  - Weis, Thomas
A1  - Morgenroth, Wolfgang
A1  - Tse, John S.
A1  - Kulik, E.
A1  - Nishiyama, Norimasa
A1  - Yavaş, Hasan
A1  - Sternemann, Christian
T1  - Persistent Octahedral Coordination in Amorphous GeO₂ Up to 100 GPa
by Kβ'' X-Ray Emission Spectroscopy
JF  - Physical Review X
N2  - We measure valence-to-core x-ray emission spectra of compressed crystalline GeO₂ up to 56 GPa and of amorphous GeO₂ up to 100 GPa. In a novel approach, we extract the Ge coordination number and mean Ge-O distances from the emission energy and the intensity of the Kβ'' emission line. The spectra of high-pressure polymorphs are calculated using the Bethe-Salpeter equation. Trends observed in the experimental and calculated spectra are found to match only when utilizing an octahedral model. The results reveal persistent octahedral Ge coordination with increasing distortion, similar to the compaction mechanism in the sequence of octahedrally coordinated crystalline GeO₂ high-pressure polymorphs.
KW  - rutile-type
KW  - glass
KW  - crystalline
KW  - pressures
KW  - complexes
KW  - silicon
KW  - oxygen
KW  - SIO₂
KW  - MO
KW  - CU
Y1  - 2019
U6  - https://doi.org/10.1103/PhysRevX.9.011025
SN  - 2469-9926
SN  - 0556-2791
SN  - 1050-2947
SN  - 1094-1622
VL  - 9
IS  - 1
PB  - American Physical Society by the American Institute of Physics
CY  - Melville, NY
ER  -