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Room-Temperature NaI/H2O Compression Icing: solute-interactions

Abstract

In situ Raman spectroscopy revealed that transiting the concentrated NaI/H2O solutions into an ice VI phase and then into an ice VII phase at 298 K proceeds in a way different from that activated by solute type. Unlike the solute type that raises both critical pressures PC1 and PC2 for the Liquid-VI and the VI-VII transition simultaneously in the Hofmeister series order: I > Br > Cl > F ~ 0, concentration increase raises the PC1 faster than the PC2 that remains almost constant at higher NaI/H2O molecular number ratios. Concentration increase moves the PC1 along the Liquid-VI phase boundary and merges to PC2 at the triple-phase junction featured at 350 K and 3.05 GPa. The highly-deformed H-O bond is less sensitive to the concentration because of the involvement of solute-solute interaction that weakens the electric field in the hydration shells. Observations confirmed that the salt solvation lengthens the O:H nonbond and softens its phonon but relaxes the H–O bond oppositely. Compression, however, has the opposite effect of salt solvation. Therefore, compression recovers the polarization-deformed O:H–O bond first and then proceeds to the phase transitions. The anion-anion interaction discriminates the effect of NaI/H2O concentration from that of solute type at an identical concentration on the phase transitions.

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Publication details

The article was received on 12 Jun 2017, accepted on 12 Sep 2017 and first published on 12 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP03919K
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Room-Temperature NaI/H2O Compression Icing: solute-interactions

    Q. Zeng, C. Yao, K. Wang, C. Sun and B. Zou, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP03919K

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