Oxygen NMR of high-density and low-density amorphous ice.

Using oxygen-17 as a nuclear probe, spin relaxometry was applied to study the high-density and low-density states of amorphous ice, covering temperatures below and somewhat above their glass transitions. These findings are put in perspective with results from deuteron nuclear magnetic resonance and with calculations based on dielectrically detected correlation times. This comparison reveals the presence of a wide distribution of correlation times.

Advances in the study of supercooled water.

In this review, we report recent progress in the field of supercooled water. Due to its uniqueness, water presents numerous anomalies with respect to most simple liquids, showing polyamorphism both in the liquid and in the glassy state. We first describe the thermodynamic scenarios hypothesized for the supercooled region and in particular among them the liquid-liquid critical point scenario that has so far received more experimental evidence.

Near-Infrared Spectra of High-Density Crystalline HO Ices II, IV, V, VI, IX, and XII.

High-pressure ice polymorphs are important for our understanding of hydrogen bonding and exist in the interior of the earth and icy moons. Nonetheless, spectroscopic information about them is scarce, where no information about their optical properties in the near-infrared (NIR) region is available at all. We here report NIR spectra of six ice polymorphs differing in terms of their density and O-atom topology, namely, ices II, IV, V, VI, IX, and XII, in comparison with the known spectra of ice I.

Calorimetric Signature of Deuterated Ice II: Turning an Endotherm to an Exotherm.

Calorimetric studies on ice II reveal a surprising HO/DO isotope effect. While the ice II to ice Ic transition is endothermic for HO, it is exothermic for DO samples. The transition enthalpies are +40 and -140 J/mol, respectively, where such a sign change upon isotope substitution is unprecedented in ice research.

Open questions on the structures of crystalline water ices.

Water can form a vast number of topological frameworks owing to its hydrogen-bonding ability, with 19 different forms of ice experimentally confirmed at present. Here, the authors comment on open questions and possible future discoveries, covering negative to ultrahigh pressures.

Thermodynamic and kinetic isotope effects on the order-disorder transition of ice XIV to ice XII.

Isotope effects accompanying the order-disorder transition of ice XIV to ice XII are studied using calorimetry, X-ray diffraction, and dielectric spectroscopy. Particular emphasis is placed on the impact of the cooling rate applied during high-pressure production and during ambient-pressure recooling on the degree of hydrogen order in the low-temperature ice XIV phase. For specimens from D2O, ordering is harder to achieve in the sense that despite smaller cooling rates, the degree of order is less than in crystals produced from H2O.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects.

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping.

Glass polymorphism in glycerol-water mixtures: II. Experimental studies.

We report a detailed experimental study of (i) pressure-induced transformations in glycerol-water mixtures at T = 77 K and P = 0-1.8 GPa, and (ii) heating-induced transformations of glycerol-water mixtures recovered at 1 atm and T = 77 K. Our samples are prepared by cooling the solutions at ambient pressure at various cooling rates (100 K s(-1)-10 K h(-1)) and for the whole range of glycerol mole fractions, χ(g).

The glass transition in high-density amorphous ice.

There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K.

Anomalously large isotope effect in the glass transition of water.

We present the discovery of an unusually large isotope effect in the structural relaxation and the glass transition temperature Tg of water. Dielectric relaxation spectroscopy of low-density as well as of vapor-deposited amorphous water reveal Tg differences of 10 ± 2 K between H2O and D2O, sharply contrasting with other hydrogen-bonded liquids for which H/D exchange increases Tg by typically less than 1 K. We show that the large isotope effect and the unusual variation of relaxation times in water at low temperatures can be explained in terms of quantum effects.