Universität zu Köln

Elbers, Mirko ORCID: 0000-0001-7800-5424, Schmidt, Christian, Sternemann, Christian ORCID: 0000-0001-9415-1106, Sahle, Christoph J., Jahn, Sandro ORCID: 0000-0002-2137-8833, Albers, Christian ORCID: 0000-0002-0526-0675, Sakrowski, Robin ORCID: 0000-0002-1561-2427, Gretarsson, Hlynur, Sundermann, Martin, Tolan, Metin and Wilke, Max ORCID: 0000-0002-1890-3940 (2021). Ion association in hydrothermal aqueous NaCl solutions: implications for the microscopic structure of supercritical water. Phys. Chem. Chem. Phys., 23 (27). S. 14845 - 14857. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 1463-9084

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Abstract

Knowledge of the microscopic structure of fluids and changes thereof with pressure and temperature is important for the understanding of chemistry and geochemical processes. In this work we investigate the influence of sodium chloride on the hydrogen-bond network in aqueous solution up to supercritical conditions. A combination of in situ X-ray Raman scattering and ab initio molecular dynamics simulations is used to probe the oxygen K-edge of the alkali halide aqueous solution in order to obtain unique information about the oxygen's local coordination around the ions, e.g. solvation-shell structure and the influence of ion pairing. The measured spectra exhibit systematic temperature dependent changes, which are entirely reproduced by calculations on the basis of structural snapshots obtained via ab initio molecular dynamics simulations. Analysis of the simulated trajectories allowed us to extract detailed structural information. This combined analysis reveals a net destabilizing effect of the dissolved ions which is reduced with rising temperature. The observed increased formation of contact ion pairs and occurrence of larger polyatomic clusters at higher temperatures can be identified as a driving force behind the increasing structural similarity between the salt solution and pure water at elevated temperatures and pressures with drawback on the role of hydrogen bonding in the hot fluid. We discuss our findings in view of recent results on hot NaOH and HCl aqueous fluids and emphasize the importance of ion pairing in the interpretation of the microscopic structure of water.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Elbers, Mirko UNSPECIFIED orcid.org/0000-0001-7800-5424 UNSPECIFIED Schmidt, Christian UNSPECIFIED UNSPECIFIED UNSPECIFIED Sternemann, Christian UNSPECIFIED orcid.org/0000-0001-9415-1106 UNSPECIFIED Sahle, Christoph J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Jahn, Sandro UNSPECIFIED orcid.org/0000-0002-2137-8833 UNSPECIFIED Albers, Christian UNSPECIFIED orcid.org/0000-0002-0526-0675 UNSPECIFIED Sakrowski, Robin UNSPECIFIED orcid.org/0000-0002-1561-2427 UNSPECIFIED Gretarsson, Hlynur UNSPECIFIED UNSPECIFIED UNSPECIFIED Sundermann, Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED Tolan, Metin UNSPECIFIED UNSPECIFIED UNSPECIFIED Wilke, Max UNSPECIFIED orcid.org/0000-0002-1890-3940 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-596799
DOI:	10.1039/d1cp01490k
Journal or Publication Title:	Phys. Chem. Chem. Phys.
Volume:	23
Number:	27
Page Range:	S. 14845 - 14857
Date:	2021
Publisher:	ROYAL SOC CHEMISTRY
Place of Publication:	CAMBRIDGE
ISSN:	1463-9084
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RAY RAMAN-SCATTERING; SODIUM-CHLORIDE; MOLECULAR-DYNAMICS; IN-SITU; ABSORPTION SPECTROSCOPY; FLUID INCLUSIONS; EARTH MATERIALS; CARBON-FIBER; PRESSURE; TEMPERATURE Multiple languages Chemistry, Physical; Physics, Atomic, Molecular & Chemical Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/59679