Probing ice VII crystallization from amorphous NaCl–D₂O solutions at gigapascal pressures

Abstract

The high density amorphous solution NaCl·10.2D2O crystallises at 260 K as almost pure ice VII during annealing at gigapascal pressures.

Quenching device for electrolytic aqueous solutions

“…We have found that concentrated NaCl solutions amorphise at ambient pressure in a high density structure similar to the HDA form of pure water [36,44], in agreement with similar observations for LiBr and LiCl solutions [45,46]. The samples produced with this device have been used in high pressure neutron diffraction studies [36,47].…”

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

“…5H2O is a clathrate similar to ice-VII but with volume expanded to 88.1 Å 3 (43) and part of the alkali-halide residing on site 6d.…”

“…We use V0, B0, and B0' of pure ice-VII from Frank et al (26). The effect of dissolved ionic species such as NaCl, KCl, and LiCl on the volume of ice-VII has been studied but different groups come to contrary conclusions whether alkali halides induce positive (27,37,43) or negative (26) excess volume.…”

Salt- and gas-filled ices under planetary conditions

“…This view was challenged almost 10 years ago, by the discovery of a high-pressure ice phase based on the ice VII lattice [16] including Li and Cl ions in the large fraction of one ion pair for each six water molecules (R = water molecules/ion pairs = 6) and showing structural and physical properties different from those of pure ice. Subsequently, LiBr and NaCl [18,19] have also been shown to form salty ice crystals under high pressure for R values close to their eutectic composition.…”

“…by crystallization upon temperature annealing of amorphous water-salt solutions at high pressure [16][17][18][19].…”