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Cation Hydration in Supercritical NaOH and HCl Aqueous Solutions
journal contribution
posted on 2017-11-21, 00:00 authored by Christoph J. Sahle, Johannes Niskanen, Christian Schmidt, Johannes Stefanski, Keith Gilmore, Yury Forov, Sandro Jahn, Max Wilke, Christian SternemannWe 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.