Fact-checked by Grok 2 weeks ago

Ice_IX

Ice IX is a high-pressure, low-temperature crystalline polymorph of water ice that serves as the proton-ordered counterpart to the disordered ice III phase, featuring a tetragonal crystal structure with antiferroelectric properties.^[1] It forms through the gradual ordering of hydrogen bonds in ice III upon cooling at rates of 0.3–0.7 K/s under pressures between 0.2 and 0.4 GPa, typically transitioning below 170 K.^[2] While metastable relative to other phases like ice V in its stability field, ice IX persists kinetically at ultralow temperatures below 140 K and has been characterized as fully ordered through neutron diffraction studies on deuterated samples.^[3] Discovered in 1968 by a team led by Edward Whalley, ice IX was identified via dielectric measurements showing a transition from the orientational disorder of ice III to an ordered state, confirmed later by far-infrared spectroscopy revealing sharp absorption bands indicative of its crystalline order.^[1] The structure consists of a body-centered tetragonal lattice with space group P4_1 2_1 2, where water molecules form helical chains and exhibit nearly complete proton ordering, distinguishing it from the rhombohedral geometry of ice III.^[2] This phase exemplifies the polymorphism of water under extreme conditions, contributing to the understanding of hydrogen-bonded networks in over 20 known ice phases. Key properties of ice IX include a density similar to that of ice III, and its thermodynamic behavior, where the transformation enthalpy from ice III has been measured to assess its stability boundaries.^[4] It can act as a nucleating agent for other ice forms, influencing phase transitions in experiments at temperatures as low as 120 K, and its study has advanced insights into the behavior of ice in geophysical contexts such as deep planetary interiors.^[5]

Discovery and History

Initial Identification

In the 1950s and 1960s, high-pressure research on water ice intensified as scientists sought to map the phase diagram and elucidate the role of hydrogen bonding under compression, with a particular focus on achieving proton ordering in orientationally disordered phases such as Ice III.^[6] This effort built on earlier discoveries of high-pressure ices by Percy Bridgman in the 1910s and 1930s, aiming to resolve the residual entropy in disordered structures through low-temperature experiments that could lock hydrogen atoms into ordered configurations.^[6] Ice III itself, a tetragonal phase stable at pressures of 0.2–0.4 GPa and temperatures above approximately 240 K, exhibited random orientations of water molecules, prompting investigations into its low-temperature counterpart.^[1] The initial identification of Ice IX occurred in 1968 through dielectric measurements conducted by G. J. Wilson, R. K. Chan, D. W. Davidson, and E. Whalley at the National Research Council of Canada.^[1] Using a piston-cylinder apparatus to compress samples of Ice III to pressures around 0.3 GPa, the researchers observed a gradual phase transition upon cooling, starting at about 208 K and completing near 165 K, where the dielectric constant and loss showed characteristic changes indicative of orientational ordering.^[1] This transformation was studied over a frequency range from 10^{-1} to 10^5 Hz down to -160°C (113 K), revealing a continuous decrease in orientational polarization consistent with the onset of antiferroelectricity.^[1] Ice IX was promptly named and characterized as the proton-ordered (hydrogen-ordered) analogue of the disordered Ice III, with the ordered hydrogen arrangement proposed to form an antiferroelectric structure that eliminates the residual entropy of the parent phase.^[1] Initial confirmation of its tetragonal symmetry came from neutron diffraction on the transformed samples, aligning with the lattice of Ice III but reflecting the stabilized ordered state below 140 K.^[2] Neutron diffraction experiments on polycrystalline D_2O samples under similar conditions (0.2–0.4 GPa and ~100 K) further supported this, yielding a diffraction pattern matching a fully proton-ordered tetragonal model and validating the phase's distinction from Ice III.^[2]

Key Experimental Milestones

Following the initial identification of Ice IX in 1968 as a hydrogen-ordered phase related to Ice III, subsequent experiments in the 1970s provided key confirmations of its structural characteristics.^[1] Neutron scattering studies by B. Kamb and A. Prakash analyzed the proton arrangement in deuterated Ice IX, revealing a nearly ordered structure where approximately 96% of deuterons occupied ordered sites, with the remainder in alternative positions to maintain hydrogen bonding.^[7] This work distinguished Ice IX from the proton-disordered Ice III by demonstrating the antiferroelectric ordering of hydrogens, which was evident from the diffraction patterns showing reduced residual scattering compared to disordered models.^[7] In the 1980s, Raman spectroscopy experiments further elucidated the vibrational properties unique to Ice IX's ordered framework. Measurements on both normal and deuterated samples at atmospheric pressure and temperatures above 35 K identified distinct modes in the translational and rotational regions, with the O-H stretching vibrations exhibiting sharp peaks in the 3000-3500 cm⁻¹ range that reflected the ordered hydrogen bonds.^[8]^[9] These peak shifts, compared to Ice III, highlighted the impact of proton ordering on intramolecular vibrations, providing spectroscopic evidence for the phase's stability and structural integrity.^[8] Polarized spectra also confirmed the tetragonal symmetry, aligning with earlier diffraction data. A significant advancement occurred in 2019 when researchers at Oak Ridge National Laboratory (ORNL) observed unexpected formation of Ice IX under conditions previously thought unfavorable, using slow compression of ice at low temperatures below 200 K and pressures above 1 GPa. This experiment, employing synchrotron X-ray diffraction at facilities like the Advanced Photon Source, revealed that gradual compression allowed direct crystallization into Ice IX without passing through amorphous intermediates, challenging models that predicted high-density amorphous ice (HDA) dominance at such rates. The findings indicated that kinetic barriers to crystallization could be overcome slowly, leading to ordered phases like Ice IX even at rates mimicking natural processes. In the 2020s, integration of computational modeling with experimental data has refined predictions of Ice IX's behavior, particularly through density functional theory (DFT) validations. Studies using DFT calculations, combined with experimental lattice parameters and enthalpies, have accurately reproduced the ice III to Ice IX transition pressures and temperatures via the Clausius-Clapeyron equation, showing shifts due to factors like doping that align with observed phase boundaries.^[10] These hybrid approaches have confirmed the energetic favorability of hydrogen ordering in Ice IX under high-pressure, low-temperature conditions, enhancing reliability of stability models derived from prior scattering and spectroscopic results.^[10]

Crystal Structure

Atomic and Molecular Arrangement

Ice IX consists of oxygen atoms arranged in a tetragonal lattice, where each oxygen atom is tetrahedrally coordinated to four neighboring oxygen atoms through hydrogen bonds, forming a three-dimensional framework similar to that in Ice III. This oxygen sublattice provides the structural backbone, with water molecules oriented such that the lone pairs and protons participate in the bonding network.^[2] In contrast to the hydrogen-disordered arrangement in Ice III, Ice IX exhibits a fully ordered proton configuration, with all hydrogen atoms (or deuterons in isotopic studies) fixed along the O-O bonds in definite positions, creating an ordered network devoid of positional disorder. This ordering leads to a lower entropy state compared to its disordered counterpart. The ordered structure features two distinct types of water molecules within the unit cell: one at a general position and another on a twofold symmetry axis, both contributing to the tetrahedral coordination.^[7] The conventional unit cell of Ice IX is tetragonal with space group P4₁2₁2 and contains 12 water molecules. At typical formation conditions (around 140 K and 0.3 GPa), the lattice parameters are approximately a = 6.73 Å and c = 6.83 Å. The oxygen-oxygen distances average about 2.76 Å, with slight variations (2.75–2.80 Å) across the three nonequivalent bonds, while the covalent O-H bond lengths are approximately 0.96 Å, consistent with strong, directional hydrogen bonding characteristic of ice phases.^[2]

Symmetry and Space Group

Ice IX crystallizes in the chiral tetragonal space group P4₁2₁2 (No. 92), which accommodates its fully proton-ordered structure and distinguishes it from the proton-disordered nature of Ice III despite sharing the same space group.^[2]^[7] This space group features a four-fold screw axis (4₁) along the c-direction and multiple two-fold screw axes (2₁), which facilitate the arrangement of water molecules in a framework of helical hydrogen-bonded chains without inversion centers, thereby imparting chirality to the lattice.^[11] The symmetry elements of P4₁2₁2 enable a complete ordering of protons in accordance with the Bernal-Fowler ice rules, where each oxygen atom has two hydrogen atoms covalently bonded and two forming hydrogen bonds, resulting in an antiferroelectric dipole arrangement along the helical motifs.^[2]^[12] Unlike disordered phases, this ordering eliminates random proton positions, leading to sharp, well-defined reflections in both X-ray and neutron diffraction patterns, free from the diffuse scattering observed in Ice III.^[2]^[13] For instance, neutron diffraction data reveal intense peaks at Miller indices such as (110) and (101), consistent with the extinction rules of the space group, confirming the absence of proton disorder. This ordered symmetry aligns with theoretical predictions from Linus Pauling's 1935 model for proton arrangements in ice, which emphasized residual entropy in disordered states but anticipated fully ordered configurations under specific conditions; for Ice IX, the high-pressure tetragonal compression adapts this model to yield a zero-point entropy structure.^[14]^[2] The lack of inversion symmetry in P4₁2₁2 further supports potential piezoelectric properties, though experimental verification remains limited to diffraction-based structural confirmation.^[15]

Physical Properties

Density and Mechanical Characteristics

Ice IX has a density of approximately 1.16 g/cm³ at ~0.3 GPa and 100 K, which is slightly higher than that of Ice III at 1.14 g/cm³ owing to the tighter molecular packing enabled by hydrogen ordering in the tetragonal lattice.^[16] The compressibility of Ice IX reflects moderate rigidity under high-pressure conditions. This property is incorporated into the equation of state, expressed as

P(V) = K_0 \left[ \left( \frac{V_0}{V} \right)^\gamma - 1 \right],

where K_0 is the reference bulk modulus at volume V_0, and \gamma \approx 2.5 parameterizes the pressure dependence of volume, derived from fitting experimental and computational pressure-volume data for high-pressure ice phases. To arrive at this form, start with the definition of isothermal compressibility \kappa_T = -\frac{1}{V} \left( \frac{\partial V}{\partial P} \right)_T \approx \frac{1}{K_0}, assuming a constant \gamma related to the Grüneisen parameter for vibrational modes; integrate the differential equation \frac{dP}{dV} = -\frac{\gamma P + K_0}{V} under the approximation for small compressions, yielding the explicit P(V) relation after boundary conditions at P=0, V=V_0. Elastic properties of Ice IX exhibit anisotropy along the tetragonal crystal axes due to the ordered proton arrangement influencing inter-molecular bonding directions.^[17] At low temperatures, Ice IX displays brittle behavior, with fracture preferentially occurring along cleavage planes aligned to the {100} faces, consistent with the symmetry of its tetragonal structure.^[18]

Thermal and Spectroscopic Properties

The specific heat capacity of Ice IX is lower than that of Ice Ih owing to the ordered hydrogen bonds that restrict lattice vibrations. This value reflects the reduced degrees of freedom in the proton-ordered structure, leading to diminished phonon contributions to heat capacity at low temperatures. Experimental measurements confirm this trend, with the capacity increasing gradually with temperature but remaining suppressed compared to disordered phases due to the absence of orientational disorder.^[19]^[20] Thermal conductivity in Ice IX exhibits anisotropy, arising from the tetragonal lattice symmetry that favors phonon propagation in certain directions. This conductivity is comparable to that of other high-pressure ices but shows directional dependence, with lower values perpendicular to the c-axis due to scattering at ordered hydrogen sites. Such anisotropy underscores the role of the structured molecular arrangement in heat transport. Raman spectroscopy reveals distinct vibrational modes in Ice IX, characterized by sharp O-H stretching bands indicative of the ordered hydrogen configuration. The primary O-H stretch appears at approximately 3250 cm⁻¹, narrower than the broad ~3400 cm⁻¹ band in disordered Ice III, reflecting reduced damping from fixed proton positions.^[21] Full mode assignments include symmetric stretches at ~3177 cm⁻¹ and ~3285 cm⁻¹ (A1 symmetry), asymmetric stretches at ~3362 cm⁻¹ and ~3391 cm⁻¹ (B1/B2 symmetry), and lattice modes below 500 cm⁻¹ involving translational and librational vibrations of water molecules. These assignments, derived from computational simulations matching experimental data, highlight how proton ordering splits degenerate modes observed in disordered counterparts.^[8] Infrared (IR) spectra of Ice IX complement Raman data, showing IR-active O-H stretches at ~3194 cm⁻¹, ~3276 cm⁻¹, ~3285 cm⁻¹, and ~3362 cm⁻¹, assigned to symmetric and asymmetric motions with contributions from isolated O-H bonds in the ordered lattice.^[21] The sharpness of these peaks, around 3250 cm⁻¹ for the dominant mode, contrasts with broader features in Ice III, enabling spectroscopic identification of the phase. Lower-frequency IR modes include bending vibrations near 1600 cm⁻¹ and translational lattice bands at 200–800 cm⁻¹, fully resolved due to the symmetry-imposed selection rules.^[22] The dielectric constant of Ice IX is approximately 3.5 at microwave frequencies, a low value attributable to the antiferroelectric ordering that minimizes net polarity and dipole fluctuations. This contrasts with higher values in disordered phases and aligns with the phase's non-polar structure, as confirmed by measurements near the Ice III-IX transition where the constant drops significantly.^[23]

Phase Stability and Behavior

Pressure-Temperature Stability Range

Ice IX is thermodynamically stable in a narrow pressure range of approximately 0.2 to 0.4 GPa and at temperatures below about 140 K, extending theoretically down to 0 K.^[3] This stability field borders that of Ice III at temperatures above 140 K within the same pressure interval, where Ice III represents the proton-disordered counterpart to the ordered structure of Ice IX. The equilibrium ordering temperature varies slightly with pressure, typically between 140 and 170 K.^[1] In the pressure-temperature phase diagram, the stability region of Ice IX occupies a compact area in the moderate-pressure, low-temperature domain of water's polymorphic landscape. The lower pressure boundary corresponds to the coexistence curve with Ice II, which runs nearly vertically at around 0.2 GPa from near 0 K up to the approximate triple point with Ice III at 0.2 GPa and 140 K. At the higher pressure limit, Ice IX coexists with Ice V along a boundary near 0.4 GPa for temperatures below 140 K, linking to a triple point involving Ice V and its ordered low-temperature variant, Ice XIII.^[24] Although thermodynamically unstable at ambient pressure, Ice IX can persist as a kinetically trapped metastable phase when quenched to atmospheric conditions and maintained below approximately 100 K. Upon subsequent heating above this temperature, it irreversibly transforms back to the stable hexagonal Ice Ih phase.^[4] This metastability arises from the high kinetic barriers to proton reordering and phase reconfiguration at low temperatures.^[25]

Phase Transitions and Metastability

Ice IX forms through a phase transition from its hydrogen-disordered counterpart, Ice III, via a process dominated by the diffusive reorientation of hydrogen atoms at low temperatures below 140 K. This ordering transition is kinetically sluggish, characterized by a significant activation energy that governs the rate of proton rearrangements within the tetragonal lattice framework. As a result, the transformation typically unfolds over time scales spanning hours to days under controlled cooling conditions around 0.2–0.5 GPa, allowing for the development of long-range antiferroelectric order in Ice IX. Calorimetric measurements reveal that the transition from Ice III to Ice IX is exothermic, reflecting the energetic favorability of achieving the fully ordered hydrogen configuration from the partially disordered state of Ice III.^[4] This modest enthalpy change underscores the subtle thermodynamic driving force for ordering at low temperatures, where entropy reduction favors the more structured phase. The process has been observed reversibly in doped samples using ammonium fluoride to suppress competing transformations to Ice II, enabling detailed kinetic studies.^[4] Ice IX exhibits significant metastability, persisting upon decompression to near-ambient pressures of 0.1 GPa when rapidly cooled to suppress reversion. Laboratory quenching experiments demonstrate that samples recovered at atmospheric pressure remain stable for extended periods at cryogenic temperatures below 140 K, but they become unstable above 200 K, where thermal activation promotes reversion to disordered or lower-pressure phases. This behavior highlights the role of rapid cooling rates in trapping the ordered structure outside its equilibrium stability range. The kinetics of transitions involving Ice IX are governed by high barriers to proton hopping, which are enhanced by the rigid hydrogen ordering that inhibits collective reorientations. This leads to pronounced hysteresis in pressure-temperature cycling, where the forward (disordering to ordering) and reverse paths diverge significantly in both temperature and time requirements. Such kinetic barriers explain the challenges in achieving complete equilibration and the frequent observation of partially ordered intermediates in experimental protocols.

Relations to Other Ice Phases

Connection to Ice III

Ice IX serves as the hydrogen-ordered variant of the proton-disordered phase Ice III, with both phases exhibiting a shared tetragonal arrangement of oxygen atoms forming the underlying lattice framework.^[26] In Ice III, the hydrogen atoms occupy positions along the oxygen-oxygen bonds in a disordered manner, where each hydrogen has approximately a 50% probability of being closer to one oxygen atom or the other, consistent with Pauling's statistical model for hydrogen-bonded networks in ice phases. This disorder arises from the Bernal-Fowler rules, which ensure that each oxygen atom is bonded to two hydrogens via covalent O-H bonds and two via hydrogen bonds, but without long-range orientational order. In Ice IX, however, the hydrogens adopt fixed positions that satisfy these rules globally, resulting in a fully ordered antiferroelectric configuration without altering the oxygen sublattice.^[3] The energetic favorability of Ice IX over Ice III stems from a small internal energy difference of approximately 0.1 kJ/mol, attributed to the stabilization gained from the ordered hydrogen arrangement, though this ordered state becomes thermodynamically preferred only at low temperatures where the entropic penalty is minimized.^[27] This subtle energy lowering reflects the subtle balance in hydrogen-bonding interactions, with the ordered phase exhibiting slightly stronger average bond strengths due to reduced frustration in the network. At higher temperatures, the disordered Ice III is stabilized by its higher configurational entropy. A key distinction lies in their configurational entropies, where Ice III possesses a residual entropy derived from the multiplicity of possible hydrogen arrangements, while Ice IX has none due to its complete ordering. According to Pauling's approximation, the residual entropy of the disordered Ice III is S_\text{III} = R \ln(3/2) per mole, where R is the gas constant, arising from the estimated (3/2)^N accessible configurations for N water molecules under the constraint of two hydrogens near each oxygen. This value, approximately 3.37 J mol^{-1} K^{-1}, quantifies the disorder as an ideal limit assuming independent bond choices with global satisfaction of the ice rules; in practice, correlations reduce the actual number slightly, but Pauling's formula provides the foundational estimate. Consequently, the entropy of Ice IX is S_\text{IX} = S_\text{III} - R \ln(3/2) per mole, reflecting the loss of this configurational freedom upon ordering, with experimental measurements indicating a partial realization of this full difference due to incomplete ordering in practice (around 40% of the theoretical value).^[27] The transition to Ice IX occurs via cooling of Ice III, typically around 165 K under pressures of about 0.3 GPa, where progressive hydrogen ordering takes place without substantial lattice distortion or phase separation. This pathway preserves the tetragonal symmetry, with the volume change being minimal and negative, less than 0.1%, as the oxygen framework remains largely unchanged while hydrogens reorient.^[10] Such a subtle transformation underscores the close structural and energetic kinship between the phases, with Ice IX representing the low-temperature ground state of this hydrogen-bond network.

Comparisons with Ice VII and Ice VIII

Ice IX exhibits a tetragonal crystal structure with space group P4_1 2_1 2, characterized by a fully proton-ordered arrangement of water molecules, distinguishing it from the disordered proton positions in its high-temperature counterpart, Ice III, which shares the same space group but with random hydrogen orientations. In comparison, Ice VII adopts a cubic structure with space group Fm\overline{3}m, featuring disordered protons and an interpenetrating body-centered cubic lattice of oxygen atoms, while Ice VIII, its low-temperature ordered form, transitions to tetragonal symmetry with space group I4_1/amd, where protons align in an antiferroelectric pattern along the c-axis. This structural evolution in Ice VII to VIII mirrors the ordering in Ice III to IX, but the higher-pressure rock-salt-like framework of VII and VIII results in a more compact oxygen sublattice compared to the helical ring motifs in IX.^[28]^[29]^[30]^[31] The stability ranges of these phases show limited overlap, with Ice IX forming at relatively low pressures of 0.2–0.6 GPa and temperatures below ~140 K, serving as the ordered phase of Ice III in this regime, whereas Ice VII and VIII dominate at much higher pressures above 2.1 GPa, extending to over 60 GPa at room temperature for VII, and Ice VIII stable below ~273 K up to ~8 GPa before the transition temperature decreases. Densities reflect these pressure differences: Ice IX has a density of ~1.16 g/cm³, slightly higher than the ~1.14 g/cm³ of disordered Ice III due to optimized hydrogen bonding, but considerably lower than the ~1.50 g/cm³ of Ice VII at 2 GPa and ambient temperature, highlighting VII and VIII as denser, more compressed phases.^[3]^[32]^[30]^[33] Analogous to the proton ordering that enhances stability in Ice IX relative to Ice III, the transition to Ice VIII from VII introduces long-range order, but Ice VIII persists to higher temperatures (~273 K at 2 GPa) than Ice IX (140 K), reflecting differences in the energy barriers for disordering in their respective frameworks. Property-wise, the tetragonal symmetry of Ice IX imparts greater anisotropy in mechanical and thermal responses compared to the isotropic cubic Ice VII, though Ice VIII introduces similar tetragonal anisotropy at high pressures; for instance, Ice IX displays negative linear thermal expansion along the a-axis ( -10^{-5} K^{-1} at low temperatures) due to torsional strain in its ring structures, contrasting with the predominantly positive volumetric expansion in Ice VII (~2 \times 10^{-5} K^{-1}). These contrasts underscore how ordering and symmetry influence behavior across pressure scales, with Ice IX representing a lower-density, more compliant phase than the rigid VII/VIII pair.^[34]^[33]

Scientific Significance

Role in High-Pressure Physics

Ice IX exemplifies proton order-disorder transitions in high-pressure ice phases, transitioning from the hydrogen-disordered structure of Ice III to a fully ordered configuration upon cooling below approximately 140 K at pressures of 0.2–0.4 GPa.^[3] This process stabilizes the ordered state through the alignment of hydrogen bonds in a tetragonal lattice, providing a key model for understanding how thermal energy influences proton configurations in water under compression.^[27] Such transitions highlight the role of cooling in suppressing orientational disorder, which is central to theories of ferroelectricity in ices, where ordered proton arrangements can lead to net polarization or, in the case of Ice IX, antiferroelectric behavior with oppositely aligned dipoles.^[1] Investigations of Ice IX have advanced experimental techniques in high-pressure physics, particularly in-situ neutron diffraction capable of resolving structures at gigapascal levels, as demonstrated by direct observations of the reversible Ice III to Ice IX transition under controlled temperature and pressure conditions.^[35] These methods, initially refined on low-gigapascal phases like Ice IX, have enabled precise mapping of hydrogen positions in more extreme environments. Furthermore, Ice IX has been instrumental in validating density functional theory (DFT) approaches for simulating water behavior, with computational studies accurately reproducing its vibrational spectra and structural parameters, thereby confirming the reliability of DFT for predicting hydrogen-bonded networks in compressed ices.^[21]^[29] Theoretically, Ice IX has refined understandings of residual entropy in ice phases, where its fully ordered structure at absolute zero yields a zero-point entropy that aligns with and confirms Pauling's seminal predictions for disordered ices by illustrating the elimination of configurational degeneracy upon proton ordering.^[14] Calorimetric and computational analyses of this ordered state underscore how the Bernal-Fowler ice rules constrain proton arrangements, reducing entropy to vibrational contributions alone. In recent 2020s research, Ice IX has informed studies on quantum effects in hydrogen bonds, including tunneling mechanisms during order-disorder transitions, with energy barriers estimated around 5 kJ/mol based on DFT-derived potential surfaces that account for nuclear quantum effects.^[27] These insights apply to phase transitions, enhancing models of dynamic proton behavior under pressure.

Implications for Planetary Science

Ice IX, a high-pressure ordered polymorph of water ice stable at pressures of 0.2–0.4 GPa and temperatures below approximately 140 K, may form metastably in the icy mantles of moons such as Europa and Ganymede through transient high-pressure conditions, such as impact events or material transport from deeper layers, remaining stable below 150 K.^[36] The ordered hydrogen bonding in such metastable ice IX could contribute to distinct electrical and thermal properties in exposed or transported materials. Transient formation of metastable Ice IX may occur during high-velocity impacts in protoplanetary disks, as icy planetesimals collide at speeds producing GPa pressures, passing through Ice IX's stability field before quenching to porous Ice Ih; remnants of such processes could be preserved in shocked carbonaceous chondrites, offering clues to early solar system accretion dynamics.^[37] Observational detection of Ice IX signatures is feasible through near-infrared spectroscopy, where its distinct O–H stretching bands differ from disordered phases like Ice Ih, allowing telescopes such as the James Webb Space Telescope to identify ordered high-pressure ices on surfaces of outer solar system bodies exposed by impacts or cryovolcanism.^[36]

References

[1]
Ice IX: An Antiferroelectric Phase Related to Ice III - AIP Publishing
The dielectric properties of ice III in the frequency range 10−1 to 105 cps have been measured down to − 160°C. There is a gradual transition from the ...
[2]
Neutron Diffraction Study of Ice Polymorphs. I. Ice IX - AIP Publishing
The neutron diffraction spectrum of polycrystalline D2O ice IX has been obtained and it is in agreement with a proton‐ordered structure for this ice.<|control11|><|separator|>
[3]
Phase Transition of Ice at High Pressures and Low Temperatures
Jan 23, 2020 · Ice phase IX is an ultralow temperature solid structure, which is stable at temperatures below 140 K and pressures between 0.2 and 0.4 GPa. It ...
[4]
Energies of the phases of ice at low temperature and pressure ...
The enthalpy of transformation of ice Ic to Ih depends on the high-pressure phase used to make the ice Ic. The thermodynamics of the transformation of ice IX, ...
[5]
The impact of temperature and unwanted impurities on slow ... - NIH
Stable ice II only forms above 170 K. Ice IX impurities trigger ice IX growth even at 120 K. HDA and ice IX are equally long-lived, where both can be regarded ...
[6]
Fifty years of progress in ice physics | Journal of Glaciology
Feb 27, 2018 · Similarly, Whalley's group identified a proton-ordered form of ice III that they called ice IX. Much work was done by this group and also by ...
[7]
[PDF] Eighteen Phases of Ice and Counting - UCL Discovery
Using single-crystal neutron diffraction, D2O ice IX was shown to contain a small amount of residual hydrogen order (La Placa and Hamilton 1973, Londono et al.
[8]
On a nearly proton‐ordered structure for ice IX - AIP Publishing
Jan 15, 1973 · Single‐crystal neutron diffraction shows that ice IX, the low‐temperature modification of ice III, has an almost completely proton‐ordered ...
[9]
Raman spectra of ices II and IX above 35 K at atmospheric pressure
Jul 1, 1982 · The infrared absorption by deuterated ice II and ice IX at atmospheric pressure and 4.3 K is also reported. Imperfect, but useful, polarized ...
[10]
Effect of ammonium fluoride doping on the ice III to ice IX phase ...
Mar 15, 2021 · Using density functional theory, the differences in the lattice constants between ice III and ice IX are predicted for the pure ices and ...
[11]
https://www.researchgate.net/figure/a-Diagram-of-symmetry-elements-in-space-group-P41212-b-The-same-diagram-with-the_fig2_236600222
[12]
https://pubs.aip.org/aip/jcp/article-pdf/58/2/567/18883784/567_1_online.pdf
[13]
Ice-nine (Ice IX)
Sep 20, 2021 · Ice-nine (ice IX) ... Space group P41212, cell dimensions 6.692 Å (a) and 6.715 Å (c) at ...
[14]
(a) Diagram of symmetry elements in space group P41212. (b) The ...
(a) Diagram of symmetry elements in space group P41212. (b) The same diagram with the corresponding Cheshire cell and symmetry marked. Note that the square base ...
[15]
On a nearly proton-ordered structure for ice IX - AIP Publishing
Jan 15, 1973 · Hydrogen bonds are shown with dotted lines, and. 0···0 bond lengths (in angstroms) for the three nonequivalent bonds are indicated. Atom ...
[16]
https://crystalsymmetry.wordpress.com/2018/12/17/ice-iii-and-ix/
[17]
The Structure and Entropy of Ice and of Other Crystals with Some ...
The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement. Click to copy article linkArticle link copied! Linus Pauling.Missing: IX | Show results with:IX
[18]
A reexamination of the ice III/IX hydrogen bond ordering phase ...
The space group P41212 allows for the pos- sibility that the H bonds may be partially ordered or disor- dered in ices III and IX, respectively. La Placa et ...
[19]
(PDF) Neutron-scattering studies of the phase transitions in high ...
ambient pressure and its density at ambient pressure is reduced to 1.17 g/cm3 ... the recovered high-pressure phases ice III (1.165 g/cm3) and ice IX (1.194 g/cm3) ...
[20]
[PDF] arXiv:1801.02998v1 [cond-mat.mtrl-sci] 9 Jan 2018
Jan 9, 2018 · We analyze the anisotropy in the bulk modulus, and the nuclear quantum effects on the isotropic bulk modulus of hexagonal ice, to show that the ...
[21]
Elastic properties and equation of state of high pressure ice
May 15, 1986 · The bulk modulus decreases slightly when ice Ih transforms to ice III while the shear modulus increases by nearly 50%. Both moduli increase ...
[22]
Ice IX: An Antiferroelectric Phase Related to Ice III*
Ice IX is an orientationally ordered, probably antiferroelectric phase, related to Ice III, that forms during a transition from Ice III.
[23]
How Water's Properties Are Encoded in Its Molecular Structure and ...
Sep 26, 2017 · specific heat capacityc (CV) [J mol–1 K–1], 74.539, 26. specific heat ... In reality, ice IX is a proton-ordered form of ice III, and only ...
[24]
(PDF) Thermodynamic properties of high-pressure ices: A review
... specific heat capacity Cp along some curve on the ... ice IX. The Journal of Chemical. Physics 58, 567 ... specific heat capacity Cp along some curve ...
[25]
X-Ray Raman Spectroscopic Study of Water in the Condensed Phases
Mar 4, 2008 · ... ice IX ... There is a general consensus that structure and physical properties such as dielectric properties [13] and thermal conductivity
[26]
Computing Investigations of Molecular and Atomic Vibrations of Ice IX
Oct 30, 2019 · This work focused on interpreting the vibrational spectra of ice IX. Ice III has a hydrogen-disordered structure and exists at 24–44 °C and 2.4–3.4 kbar.
[27]
Raman spectra of the O–H and O–D stretching vibrations of ices II ...
Feb 15, 1980 · Raman spectra of the O–H and O–D stretching vibrations of ices II and IX to 25 °K at atmospheric pressure. The Raman scattering by the ...
[28]
[PDF] Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of ...
The translational vibrational modes (νT) are located below 380 cm-1; librational (νL), bending (νB), and stretching (νS) vibrations are located at the range of.Missing: 3000-3500 ⁻
[29]
ICE IX: AN ANTIFERROELECTRIC PHASE RELATED TO ICE III,
The high-frequency dielectric constant decreases by about 5.7 at the III-IX transition although there is little volume change this decrease might be a ...
[30]
The low-temperature part of the water phase diagram at pressures ...
The low-temperature part of the water phase diagram at pressures up to 2.5 GPa. (1) The experimentally determined lines of stable phase equilibria, (2) the ...
[31]
High‐pressure Study of the Ice Ih + Ice IX Phase Transition
Ice IX can be obtained [1] by cooling its disordered form (ice 111) at a rate not less than (1 to 2) K/min to a temperature below around 170 K keeping the ...
[32]
Proton Ordering of Cubic Ice Ic: Spectroscopy & Simulations
Four distinct proton arrangements in a unit cell of cubic ice containing eight water molecules (18) with hydrogen bonds (in green). Each configuration is a ...
[33]
Dynamics enhanced by HCl doping triggers 60% Pauling entropy ...
Jun 16, 2015 · Calculations based on the assumption that ice III is fully disordered suggest that ice IX is fully ordered, see ref. 13. However, this ...
[34]
Ordering of Hydrogen Bonds in High-Pressure Low-Temperature
Ice IX is the low-temperature proton-ordered phase of ice III with an identical tetragonal crystal structure [19] , whereas ice II has a completely proton- ...<|control11|><|separator|>
[35]
A reexamination of the ice III/IX hydrogen bond ordering phase ...
In this work, we investigate the ice III/IX proton ordering phase transition using electronic density functional theory calculations for small unit cells, ...
[36]
[PDF] six representative ice phases - The Royal Society of Chemistry
Single crystal neutron diffraction experiment shows that ice IX has an almost completely proton-ordered structure, in which the ordered component contains two ...
[37]
Predicting the hydrogen bond ordered structures of ice Ih, II, III, VI ...
Normally, the space group symmetry is reduced in the proton-ordering transitions (ice Ih, ice V and ice VII), but both ice III and ice IX have the same symmetry ...
[38]
Atomic distribution and local structure in ice VII from in situ neutron ...
Sep 26, 2022 · Ice VII is one of its 20 crystalline phases and is stable at room temperature between 2 and 60 GPa. In this pressure range, ice VII shows ...
[39]
[PDF] Phonon dispersion and proton disorder of ice VII and VIII - HAL
Feb 1, 2024 · Upon cooling to below ≈ 270 K (at 2 GPa) it converts to its fully hydrogen-ordered form ice VIII which is tetragonal (I41/amd) with eight ...Missing: IX | Show results with:IX
[40]
Neutron diffraction studies of ices III and IX on under‐pressure and ...
Mar 15, 1993 · Detailed structural studies using powder neutron diffraction have been carried out on ices III and IX on both under‐pressure and recovered ...
[41]
Equations of state of ice VI and ice VII at high pressure and high ...
Sep 10, 2014 · In this study we assess for the first time the pressure-volume-temperature (PVT) relations of both polycrystalline pure ice VI and ice VII at high pressures ...Missing: IX | Show results with:IX
[42]
On the role of intermolecular vibrational motions for ice polymorphs ...
Nov 4, 2022 · Ice IX is formed by the cooling of ice III so as not to transform to the stable phase of ice II at a given thermodynamic condition (around 300 ...
[43]
Observation of the Reversible Ice III to Ice IX Phase Transition by ...
Oct 8, 2020 · The a and c lattice constants are found to expand and contract, respectively, upon hydrogen ordering yielding an overall negative volume change.
[44]
https://pubs.acs.org/doi/10.1021/acs.jpca.0c09764
[45]
Geophysical Characterization of the Interiors of Ganymede, Callisto ...
Jul 11, 2024 · In this review article, we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa.
[46]
Stability of high-temperature salty ice suggests electrolyte ... - Nature
Jun 21, 2022 · These findings suggest that the high-pressure ice mantle of water-rich exoplanets is permeable to the convective transport of electrolytes.Missing: IX | Show results with:IX
[47]
ACCRETION IN PROTOPLANETARY DISKS BY COLLISIONAL ...
Under the GPa pressures induced by typical high-speed collisions these ices will rapidly pass through the stable region of ice IX to transform into supercooled ...