Microscopic structure of water at elevated pressures and temperatures

Sahle, Christoph J.; Sternemann, Christian; Schmidt, Christian; Lehtola, Susi; Jahn, Sandro; Simonelli, Laura; Huotari, Simo; Hakala, Mikko; Pylkkänen, Tuomas; Nyrow, Alexander; Mende, Kolja; Tolan, Metin; Hämäläinen, K.; Wilke, Max

doi:10.1073/pnas.1220301110

Cited by 136 publications

(103 citation statements)

References 74 publications

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“…46,56−66 Although the correlations are not straightforward, it has been shown that the pre-edge is sensitive to the number of hydrogen bonds. 46,[58][59][60]62,63,65 Especially the differences in the donating hydrogen bonds affect the pre-edge. 63 The intensity in the postedge area is related to tetrahedral ordering of the system.…”

Section: ■ Methodsmentioning

confidence: 99%

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid

et al. 2015

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Hydration of sulfuric acid plays a key role in new-particle formation in the atmosphere. It has been recently proposed that proton dynamics is crucial in the stabilization of these clusters. One key question is how water molecules mediate proton transfer from sulfuric acid, and hence how the deprotonation state of the acid molecule behaves as a function concentration. We address the proton transfer in aqueous sulfuric acid with O K edge and S L edge core-excitation spectra recorded using inelastic X-ray scattering and with ab initio molecular dynamics simulations in the concentration range of 0-18.0 M. Throughout this range, we quantify the acid-water interaction with atomic resolution. Our simulations show that the number of donated hydrogen bonds per Owater increases from 1.9 to 2.5 when concentration increases from 0 to 18.0 M, in agreement with a rapid disappearance of the pre-edge feature in the O K edge spectrum. The simulations also suggest that for 1.5 M sulfuric acid SO4(2-) is most abundant and that its concentration falls monotonously with increasing concentration. Moreover, the fraction of HSO4(-) peaks at ∼12 M.

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Section: ■ Methodsmentioning

confidence: 99%

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid

et al. 2015

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“…We assign the components C2 and C3 at ~3450 cm -1 and ~3580 cm -1 to ν 1 and ν 3 of H 2 O monomers (e.g., Walrafen, 1962). The component C1 at ~3280 cm -1 is assigned to O-H stretching vibrations of strongly hydrogen-bonded, polymerised water species because the relative intensity of this component correlates with the dependence of polymerisation on pressure and temperature (e.g., Sahle et al, 2013) and decreases with addition of salt (e.g., Walrafen, 1962).…”

Section: Compression-enhanced Contact Ion Pairingmentioning

confidence: 99%

Pressure-induced ion pairing in MgSO4 solutions: Implications for the oceans of icy worlds

Schmidt¹,

Manning²

2016

Geochem. Persp. Let.

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At ambient temperature, liquid water transforms from a low-density to a high-density dynamic structure at ~0.2 GPa. The transition persists in electrolyte solutions; however, its effects on solute properties are unknown. We obtained Raman spectra of 0.5-2.0 molal MgSO 4 solutions at 21 °C and 10 -4 to ~1.6 GPa. Above about 0.4 GPa, we observed an increase in the MgSO 4 contact ion pair abundance with pressure, regardless of concentration. This phenomenon contravenes the general rule that dissolved salts dissociate upon compression, and is likely caused by the structural collapse in the solvent with pressure due to increased hydrogen-bond breaking. Increasing ion association in high-pressure aqueous solutions implies that, at a given salinity, high-density water in deep, cold planetary oceans and pore waters will possess lower ionic strength and electric conductivity than previously thought. This behaviour will also lead to higher ocean salinity in the interiors of Pluto and the largest icy moons of Jupiter and Saturn, Ganymede, Callisto, and Titan, or in exoplanet water-worlds, through enhancement of submarine silicate weathering.

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“…[26]. Experimental studies have provided insights for the structure of near-critical water [33,34]; however, there has been relatively little theoretical work on thermophysical properties of bulk water near the critical point.…”

Section: Introductionmentioning

confidence: 99%

Thermophysical properties of supercritical water and bond flexibility

Shvab

Sadus

2015

Phys. Rev. E

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Molecular dynamics results are reported for the thermodynamic properties of supercritical water using examples of both rigid (TIP4P/2005) and flexible (TIP4P/2005f) transferable interaction potentials. Data are reported for pressure, isochoric and isobaric heat capacities, the thermal expansion coefficient, isothermal and adiabatic compressibilities, Joule-Thomson coefficient, speed of sound, self-diffusion coefficient, viscosities, and thermal conductivity. Many of these properties have unusual behavior in the supercritical phase such as maximum and minimum values. The effectiveness of bond flexibility on predicting these properties is determined by comparing the results to experimental data. The influence of the intermolecular potential on these properties is both variable and state point dependent. In the vicinity of the critical density, the rigid and flexible potentials yield very different values for the compressibilities, heat capacities, and thermal expansion coefficient, whereas the self-diffusion coefficient, viscosities, and thermal conductivities are much less potential dependent. Although the introduction of bond flexibility is a computationally expedient way to improve the accuracy of an intermolecular potential, it can be counterproductive in some cases and it is not an adequate replacement for incorporating the effects of polarization.

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Microscopic structure of water at elevated pressures and temperatures

Cited by 136 publications

References 74 publications

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid

Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid

Pressure-induced ion pairing in MgSO4 solutions: Implications for the oceans of icy worlds

Thermophysical properties of supercritical water and bond flexibility

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