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We report compression and decompression experiments of hexagonal ice in a piston cylinder setup in the temperature range of 170–220 K up to pressures of 1.6 GPa. The main focus is on establishing the effect that an increase in compression rate up to 4000 MPa/min has on the phase changes incurred at high pressures. While at low compression rates, a phase change to stable ice II takes place (in agreement with earlier comprehensive studies), we find that at higher compression rates, increasing fractions and even pure ice III forms from hexagonal ice. We show that the critical compression rate, above which mainly the metastable ice III polymorph is produced, decreases by a factor of 30 when decreasing the temperature from 220 to 170 K. At the highest rate capable with our equipment, we even find formation of an ice V fraction in the mixture, which is metastable with respect to ice II and also metastable with respect to ice III. This indicates that at increasing compression rates, progressively more metastable phases of ice grow from hexagonal ice. Since ices II, III, and V differ very much in, e.g., strength and rheological properties, we have prepared solids of very different mechanical properties just by variation in compression rate. In addition, these metastable phases have stability regions in the phase diagrams only at much higher pressures and temperatures. Therefore, we anticipate that the method of isothermal compression at low temperatures and high compression rates is a tool for the academic and industrial polymorph search with great potential. [ABSTRACT FROM AUTHOR]

An understanding of water’s anomalies is closely linked to an understanding of the phase diagram of water’s metastable noncrystalline states. Despite the considerable effort, such an understanding has remained elusive and many puzzles regarding phase transitions in supercooled liquid water and their possible amorphous proxies at low temperatures remain. Here, decompression of very high density amorphous ice (VHDA) from 1.1 to 0.02 GPa at 140 K is studied by means of dilatometry and powder x-ray diffraction of quench-recovered states. It is shown that the three amorphous states of ice are reversibly connected to each other, i.e., LDA↔e-HDA↔VHDA. However, while the downstroke VHDA→e-HDA transition takes place in the pressure range of 0.06 GPa≤p≤0.40 GPa, the e-HDA→LDA transition takes place quasi-discontinuously at p∼0.06 GPa. That is, two amorphous-amorphous transitions of a distinct nature are observed for the first time in a one-component system–a first-order-like transition (e-HDA→LDA) and a transition which is not first-order like but possibly of higher order (VHDA→e-HDA). VHDA and e-HDA are established as the most stable and limiting states in the course of the transition. We interpret this as evidence disfavoring the hypothesis of multiple first-order liquid-liquid transitions (and the option of a third critical point), but favoring a single first-order liquid-liquid transition (and the option of a second critical point). [ABSTRACT FROM AUTHOR]

High-density amorphous ice was heated at constant pressures of between 0.52 to 1.9 GPa from 77 K up to 240 K. The formed phases were characterized by x-ray diffractograms of samples recovered under liquid N[sub 2] at 1 bar. The (meta)stability domain of ice XII thus revealed extends between ;≈158-212 K from ≈0.7 to ≈1.5 GPa. We further discuss whether ice XII has a low-temperamre region of stability within the ice VI domain. Our (meta)stability domain of ice XII is in a different region of water's phase diagram than that shown by Koza et al. [Phys. Rev. Lett. 84, 4112 (2000)]. [ABSTRACT FROM AUTHOR]

Presents a study which described a method for the vitrification of pure liquid water and dilute aqueous solutions, the only one without a liquid cryomedium for heat transfer. Uses of the method; Fields in which the method can be applied; Implication of the success in the vitrification of liquid water.

Crystallization kinetics of hyperquenched D2O liquid has been studied by Fourier transform infrared spectroscopy by determining the irreversible change in the spectra of stretching vibrations of the decoupled OH oscillator in ≊12 mol % HOD in D2O. The kinetics follows an almost exponential behavior with time. The exponent to the crystallization time, n, increases from its value of 1.0 at 152 K to 1.2 at 147 K and its value is slightly lower than that of H2O. The combined results of H2O and D2O indicate that temperature rather than the mass of the molecules determines n. Interpretation of n in terms of the morphology of grains formed seems inconsistent in view of the observed temperature effect. It is suggested that an alternative interpretation of n in terms of distribution of diffusion times, or time independent activation energy (barrier height to crystallization), is more appropriate. Calorimetric measurements for the crystallization of H2O yield results consistent with those from infrared spectroscopic study. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Metastable liquid water, obtained by heating its hyperquenched glassy state above its glass→liquid transition temperature, crystallizes to cubic ice. Kinetics of this crystallization has been studied by Fourier transform infrared spectroscopy by determining the change in the spectra of stretching vibrations of the decoupled OD oscillator in 3.6 mole % HOD in H2O. The crystallization kinetics follows the equation x=[1-exp(-ktn)] and is diffusion controlled. Annealing at a temperature below its glass→liquid transition temperature alters this kinetics as the grain–growth process begins to control the early stages of crystallization. [ABSTRACT FROM AUTHOR]

The dielectric permittivity and loss tangent of hyperquenched glassy water (HGW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature and corresponding measurements have been made of the crystallized forms. The effect of thermal cycling has been investigated. Except for a shoulder at Tg for 10 kHz measurement, there are no features in the loss tangent until the beginning of crystallization when the increase in tan δ of the water above Tg is dominated by the decrease on the formation of cubic ice and a peak appears. The dielectric loss of HGW at 80 K is ≊5 times more than that of cubic ice formed on crystallization by heating to 195 K and 2.8 times higher at Tg. The dielectric loss of the cubic ice formed on crystallization tends towards a plateau value prior to rapidly increasing with increasing temperature, which is evidence for a low temperature relaxation which vanishes on conversion to hexagonal ice. The plateaulike region indicates the presence of topologically disordered structure of intergranular water. The loss tangent lacks any feature that can be attributed to the presence of ‘‘dangling’’ OH groups. A comparison of these results with those of in vacuo sintered vapor-deposited amorphous solid water (ASW) [Johari et al., J. Chem. Phys. 95, 2955 (1991)] shows that the presence of ≊5% cubic ice in HGW causes its crystallization to occur more rapidly, leading to larger grains or less intergranular space and a lower value of dielectric loss of the cubic ice formed by heating it, than that formed by heating ASW. Implications of these results for the heat evolved in the phase transformation process have been discussed. [ABSTRACT FROM AUTHOR]

Amorphous solid D2O from hexagonal and cubic ices and H2O from (HF, NH3, and NH4F) doped hexagonal ice have been prepared by Whalley’s method, and their thermal behavior has been investigated by differential scanning calorimetry from 103 to 250 K. For a heating rate of 30 K min-1 , the temperature of the onset of the reversible glass[larger_closed_square]liquid transition, Tg, is raised by about 4 K when H2O is substituted by D2O. Doping with NH3 and NH4F causes little change in Tg but with HF Tg becomes undetectable. The increase in heat capacity at Tg is reduced by about a factor of 3 on deuteration but marginal changes occur on doping with NH3 or NH4F. The increase in Tg on deuteration is ≊4 times of that observed for the amorphous forms made from the vapor and the liquid, and more than twice of that expected from isoviscous or isorelaxational states, assuming that the functional form of the molecular reorientation rates with temperature is unaffected by isotopic substitution. NH3 and NH4F as dopants, which generally increase the reorientation rate of water molecules in hexagonal and cubic ices, have no detectable effect on the calorimetric relaxation rate of the pressure-amorphized forms, thus indicating that the increase in the concentration of Bjerrum defects for these two dopants does not alter Tg. All these observations suggest that the structure of pressure-amorphized solids is topologically different from that of the amorphous forms made from the vapor and the liquid. [ABSTRACT FROM AUTHOR]

The dielectric permittivity and loss of vapor-deposited amorphous solid water (ASW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature. Similar measurements have also been made on the cubic ice formed after the crystallization of ASW and the hexagonal ice formed on heating the cubic ice. The loss tangent shows a broad sub-Tg relaxation peak centered at about 100 K and an approach towards a plateau value which appears as a shoulder. The peak is attributed to thermally activated rotation of H2O molecules with one or two dangling OH groups on the surface of the pores of the microporous sample, and the shoulder to localized motions within the network structure. Sintering of the samples on thermal cycling between 77 and ≊120 K in vacuo causes the broad peak to vanish. With increase in temperature, above Tg, the loss tangent shows the emergence of the expected α-relaxation peak of a liquid at T>Tg, whose completion is terminated by the onset of crystallization to cubic ice at about the same temperature for 1 kHz and for 10 kHz measurements. Thereafter, crystallization becomes slower, thus allowing further observation of the low-temperature part of the α-relaxation peak.The dielectric loss of amorphous solid water at 80 K is nearly 20 times that of the cubic ice formed on its crystallization after heating to 193 K, and nearly 3.5 times higher at Tg. The dielectric loss of the cubic ice formed on crystallization tends towards a plateau value prior to rapidly increasing with increase in temperature, an evidence for a low temperature relaxation which vanishes on conversion to hexagonal ice. This relaxation indicates a remnant topologically disordered structure of intergranular water and/or stacking faults in cubic ice. Samples sintered by thermal cycling in vacuo to ≊120 K crystallized in one step, whereas those without prior thermal cycling crystallized in two steps to cubic ice. Annealing of the... [ABSTRACT FROM AUTHOR]

The thermal behavior of hyperquenched glassy D2O was investigated by differential scanning calorimetry from 103 to 250 K, in order to investigate the isotope effect on the glass→liquid transition and on the liquid to cubic, and cubic to hexagonal ice. For a heating rate of 30 K min-1 the temperatures of the thermal effects are: 137 K for the onset of the reversible glass→liquid transition (Tg), 154 and 173 K for the beginning and the peak minimum of the crystallization exotherm, and ≊229 K for the peak minimum of the transformation cubic→hexagonal ice. Increase in heat capacity at Tg and the width of the glass transition are similar to those reported for glassy H2O. Tg of D2O is higher than that of H2O by an amount that is expected for isorelaxational and/or isoviscous states assuming that the functional form of the molecular reorientation rates with temperature is unaffected by the isotopic substitution. The increase in the temperature of crystallization of ‘‘fluid’’ D2O is ≊three times greater than the increase in the glass→liquid transition which causes Tg and devitrification to become more separated in D2O than in H2O. Implications of these results for both the inferred λ-type anomally at ≊228 K in H2O and at ≊233 K in D2O, and the presumed formation of a gel-like structure at these temperatures are discussed. [ABSTRACT FROM AUTHOR]

Presents a study which focused on the bandwidth of the decoupled O-D oscillator in amorphous solid water and its dependence on deposition conditions and temperature. Relationship between bandwidth and temperature; Methods; Results and discussion.

Many acronyms are used in the literature for describing different kinds of amorphous ice, mainly because many different preparation routes and many different sample histories need to be distinguished. We here introduce these amorphous ices and discuss the question of how many of these forms are of relevance in the context of polyamorphism. We employ the criterion of reversible transitions between amorphous “states” in finite intervals of pressure and temperature to discriminate between independent metastable amorphous “states” and between “substates” of the same amorphous “state”. We argue that the experimental evidence suggests we should consider there to be three polyamorphic “states” of ice, namely low-(LDA), high-(HDA) and very high-density amorphous ice (VHDA). In addition to the realization of reversible transitions between them, they differ in terms of their properties, e.g., compressibility, or number of “interstitial” water molecules. Thus they cannot be regarded as structurally relaxed variants of each other and so we suggest considering them as three distinct megabasins in an energy landscape visualization. [ABSTRACT FROM AUTHOR]

A range of techniques has so far been employed for producing amorphous aqueous solutions. In case of aqueous tetrahydrofuran (THF) this comprises hyperquenching of liquid droplets, vapour co-deposition and pressure-induced amorphization of the crystalline cubic structure II clathrate. All of these samples are thermally labile and crystallize at temperatures above 110 K. We here outline a variant of the pressure-amorphization protocol developed by Suzuki [Phys. Rev. B, 2004, 70, 172108], which results in a highly crystallization resistant amorphous THF hydrate. The hydrate produced according to our protocol (annealing to 180 K at 1.8 GPa rather than to 150 K at 1.5 GPa) does not transform to the cubic structure II THF clathrate even at 150 K. We track the reason for this higher stability to the presence of crystalline remnants when following the Suzuki protocol, which are removed when using our protocol involving higher pressures and an annealing step. These crystalline remnants later serve as crystallization seeds lowering the thermal stability of the amorphous sample. Our protocol thus makes a purely amorphous THF hydrate available to the research community. We use powder X-ray diffraction to study the process of nucleation and slow crystal growth in the temperature range 160–200 K and find that the local cage structure and periodicity of the fully crystalline hydrate develops even at the earliest stages of crystallization, when the “clathrate crystal” has a size of about two unit cells. [ABSTRACT FROM AUTHOR]

Polar stratospheric clouds (PSCs) are extremely efficient at catalysing the transformation of photostable chlorine reservoirs into photolabile species, which are actively involved in springtime ozone-depletion events. Why PSCs are such efficient catalysts, however, is not well understood. Here, we investigate the freezing behaviour of ternary HNO3–H2SO4–H2O droplets of micrometric size, which form type II PSC ice particles. We show that on freezing, a phase separation into pure ice and a residual solution coating occurs; this coating does not freeze but transforms into glass below ∼150 K. We find that the coating, which is thicker around young ice crystals, can still be approximately 30 nm around older ice crystals of diameter about 10 µm. These results affect our understanding of PSC microphysics and chemistry and suggest that chlorine-activation reactions are better studied on supercooled HNO3–H2SO4–H2O solutions rather than on a pure ice surface. [ABSTRACT FROM AUTHOR]

- A dispersive model of radical accumulation in irradiated solids is discussed by the example of hexagonal ice (Ih) and cubic ice (Ic) obtained by annealing of hyperquenched glassy water at 160 K. The model assumes that radical production upon γ-irradiation is accompanied by their second-order decay, which proceeds according to dispersive kinetics with the time-dependent specific reaction rate k(t) = Bt[sup α-1], where B = constant and α is the dispersion parameter equal to 0.40 for both the hexagonal and cubic ices. The radicals, OH in Ih, and OH plus HO[sub 2] in Ic are produced at the same rate upon γ-irradiation. The observed enhancement of radical accumulation in ice Ic in comparison with Ih is due to the marked decrease of radical recombination in ice Ic. This is rationalized by the hindrance of radical transport in the lattice of ice Ic containing substantial amounts of Bjerrum-type L-defects. [ABSTRACT FROM AUTHOR]

Polycrystalline hexagonal ice containing thymine was γ-irradiated at 77 K, and X-band electron paramagnetic resonance spectra of the resulting radicals were recorded at this temperature immediately after irradiation, and after thermal annealing of the samples at temperatures up to 250 K. The examined frozen samples were obtained from hyperquenched glassy aqueous solution containing 0.005 M of thymine, by using two different procedures: (i) crystallization of the glass by heating up to 250 K, and (ii) warming the glass up to room temperature to melt it, and subsequent cooling of the solution in liquid N2. Thymine-derived radicals were detectable only in the samples obtained by crystallization of the glass. We conclude that the extent of solute segregation is less for the frozen aqueous solution made by route (i) than by route (ii). Therefore, the solute is more hydrated in the frozen sample made by route (i) and the primary products of water radiolysis can react with the solute. The present results are compared with those reported for the thymine/hyperquenched glassy water system (Bednarek et al. , J. Phys. Chem. B 103 , 6824 (1999)). [ABSTRACT FROM AUTHOR]

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

States that calorimetric observations of the structural relaxation which is characteristic of a glass demonstrate that hyper-quenched solid water is amorphous.

Presents information on a study which investigated type I isotherms for N [sub2] adsorption on vapor deposited amorphous solid water. Method of the study; Results and discussion.

Presents an erratum for an article on the kinetics of crystallizing water near 150K by Fourier transform infrared spectroscopy.