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Ice_VII

Ice VII is a high-pressure polymorph of water ice characterized by a body-centered cubic (bcc) lattice of oxygen atoms, in which each oxygen is covalently bonded to two hydrogen atoms and forms hydrogen bonds with two more, resulting in a proton-disordered configuration with tetrahedral coordination.^[1] This phase forms under extreme compression of liquid water, typically at pressures above 2 GPa, and remains stable up to approximately 60 GPa at room temperature, encompassing a wide range of conditions relevant to planetary interiors.^[1]^[2] Unlike ordinary ice Ih, Ice VII exhibits high density (about 1.65 g/cm³ at 2.5 GPa and room temperature) and isotropic properties due to its cubic symmetry, with elastic moduli increasing nonlinearly with pressure, such as the adiabatic bulk modulus following K_S = 4.0(2) + 8.51(4)P - 0.081(2)P^2 + 5.2(4) \times 10^{-4}P^3 (with P in GPa).^[1] Ice VII was first identified in the 1960s through high-pressure experiments using opposed anvils probing the dielectric properties of compressed ice, revealing its transition to a new ordered phase, Ice VIII, at lower temperatures around 0°C.^[3] It nucleates rapidly—within nanoseconds—under shock or ramp compression of liquid water, often via homogeneous mechanisms in bulk samples or heterogeneous growth on surfaces, driven by extreme undercooling without a preceding heat layer.^[2] At higher pressures near 58 GPa, it transitions to the dynamically disordered Ice X, where protons become centered between oxygens.^[1] In planetary contexts, Ice VII is inferred to exist in the mantles of ice giants like Uranus and Neptune, as well as in "ocean world" exoplanets, influencing thermal transport and material differentiation due to its high compressibility and moderate thermal conductivity.^[2] A notable variant, plastic Ice VII, was experimentally confirmed in 2025 using quasi-elastic neutron scattering, representing a hybrid solid phase where the bcc crystalline structure persists but water molecules undergo rapid, liquid-like rotational diffusion on picosecond timescales (e.g., reorientational time of ~0.51 ps at 518 K and 5.5 GPa).^[4] This plastic behavior emerges along the Ice VII melting line at pressures of 3–6 GPa and temperatures of 450–600 K, featuring jump-rotor dynamics with C4 rotations and elevated hydrogen vibrational amplitudes (~0.80 Å²), distinguishing it from the rigidly oriented molecules in standard Ice VII.^[4]^[5] Such properties suggest plastic Ice VII could facilitate plastic flow and enhanced heat conduction in the deep interiors of icy bodies, with potential detectability via far-infrared spectroscopy due to distinct vibrational spectra.

History

Discovery

Ice VII was first discovered in 1937 by American physicist Percy W. Bridgman during piston-cylinder compression experiments on water, where he identified a new high-pressure solid phase emerging from the liquid at pressures exceeding approximately 22 kbar (2.2 GPa) near room temperature. Bridgman designated this phase as ice VII, following his established Roman numeral numbering system for water polymorphs, which sequentially labeled distinct ice forms based on their order of discovery under progressively higher pressures—a convention that facilitated the organization of high-pressure phase research. This system originated from Bridgman's earlier investigations starting in 1912, where he systematically explored water's behavior up to 12,000 kg/cm², identifying initial phases like ice II and III, and expanded it with subsequent work to encompass more complex high-pressure ices. Bridgman's initial detection relied on volumetric and thermal measurements rather than direct structural analysis, noting ice VII's higher density compared to preceding phases and its stability up to at least 45,000 kg/cm² along certain isotherms. These experiments highlighted ice VII's distinction from ice VI, which forms at lower pressures around 1 GPa, with the transition boundary observed near 22 kbar under ambient conditions, marking a reversible phase change characterized by a small volume decrease. Confirmation of ice VII's crystal structure occurred in the mid-20th century through X-ray diffraction studies on quenched samples. In the 1950s and 1960s, researchers employed powder X-ray techniques to probe recovered high-pressure ices, revealing ice VII's cubic symmetry with a body-centered arrangement of oxygen atoms, consistent with space group Pn3m. A pivotal 1964 study by Barclay Kamb and Briant L. Davis provided the first detailed diffraction data, indexing the pattern to a cubic lattice parameter of about 3.28 Å at ambient conditions post-quenching, unequivocally distinguishing ice VII from the tetragonal ice VI by its higher symmetry and proton disorder. Subsequent key experiments in this era refined the ice VI-to-VII transition pressure to 2.1–2.5 GPa, depending on temperature, through careful piston-cylinder runs and calorimetric measurements that captured the phase boundary's slope in the pressure-temperature diagram. For example, 1968 work by Pistorius et al. used differential thermal analysis to map the transition up to 5 GPa, confirming ice VII's broader stability field and its role as a high-density phase in water's complex polymorphism. These efforts established ice VII as a robust, experimentally reproducible polymorph central to early high-pressure physics.

Recognition as a Mineral

In 2018, researchers reported the discovery of Ice VII as microscopic inclusions within ultra-deep diamonds sourced from subduction zones, marking the first confirmed natural occurrence of this high-pressure ice phase.^[6] These diamonds, originating from mantle depths ranging from approximately 400 to 800 km, contained Ice VII trapped during the diamonds' formation in water-rich environments.^[6] The inclusions were analyzed using synchrotron X-ray diffraction at facilities like the Advanced Photon Source, which revealed the characteristic body-centered cubic structure of Ice VII, confirming its identity despite the extreme pressures under which it formed.^[6] This finding prompted the formal recognition of Ice VII as a mineral species by the International Mineralogical Association (IMA) under designation 2017-029, approved in August 2017 and published in the CNMNC Newsletter.^[7] As the first naturally occurring high-pressure ice phase to receive IMA approval, Ice VII—chemically H₂O and structurally distinct from common ice polymorphs—highlighted its stability in deep Earth conditions.^[7]^[6] Although Ice VII had been synthesized in laboratories since the mid-20th century, its presence in natural samples validated theoretical models of its behavior under mantle pressures.^[6] The recognition of Ice VII carries significant implications for understanding the water cycle in Earth's mantle, providing direct evidence of free aqueous fluids persisting at extreme depths beyond the typical stability limits of liquid water.^[6] These fluids, likely derived from subducted oceanic crust, suggest localized saturation and mobility of water in the transition zone, influencing mantle dynamics, volatility transport, and potentially deep seismicity.^[6] Such discoveries underscore the role of high-pressure ices in geochemical processes within subduction environments.^[6]

Structure

Crystal Structure

Ice VII exhibits a body-centered cubic (BCC) arrangement of oxygen atoms, forming a lattice with space group Pn3m (No. 224).^[8] In this structure, each oxygen atom is coordinated by eight equidistant neighboring oxygens, characteristic of the BCC symmetry, with the unit cell containing two water molecules.^[9] This cubic framework provides the foundational scaffold for the phase's high-pressure stability.^[10] The hydrogen atoms in Ice VII form two interpenetrating but non-interconnected networks of hydrogen bonds, akin to two independent cubic ice lattices offset from one another.^[11] At room temperature, these hydrogen positions are positionally disordered, with protons randomly occupying sites along the midpoints of the oxygen-oxygen bonds, satisfying the ice rules where each oxygen donates two hydrogens and accepts two.^[8] This disorder arises from the high entropy of the proton configurations, which is a key feature distinguishing Ice VII from lower-pressure ices. Neutron diffraction studies have been instrumental in probing the hydrogen sublattice, revealing that the oxygen-oxygen distance is approximately 2.8 Å at the formation pressure near 2 GPa, with hydrogen positions inferred from the scattering patterns of deuterated samples. These measurements confirm the average bond geometry while highlighting the dynamic nature of the disorder.^[8] A 2025 study employing Hirshfeld atom refinement on single-crystal X-ray diffraction data further validated this disorder, providing precise hydrogen atom positions and bond lengths under compression in the 1.8–2.6 GPa range, with refined O-H distances around 0.94 Å.^[10] This refinement technique, which models aspherical electron densities, offered unprecedented accuracy for the disordered hydrogens without relying on neutron data.^[12] The BCC oxygen lattice of Ice VII bears resemblance to that in BCC metals, such as iron or tungsten, where the close-packed coordination enhances mechanical stability under pressure.^[9] However, the positional disorder of the hydrogens in Ice VII introduces additional entropic stabilization, facilitating rapid crystal growth rates comparable to those in metallic systems and contributing to the phase's persistence in high-pressure environments.^[11] This disorder-metal analogy underscores how molecular complexity modulates the lattice's response to compression.^[13]

Density

Ice VII has a density of approximately 1.65 g/cm³ at the transition pressure of 2.2 GPa and 355 K, marking the boundary for its formation from ice VI. This value represents the initial density at the lower end of its stability field under those conditions.^[14] The pressure-dependent density of Ice VII can be approximated by the linear relation ρ(P) ≈ ρ₀ + κP near the transition, where κ ≈ 0.07 g/cm³/GPa up to 10 GPa, though more advanced equations of state, such as the Birch-Murnaghan form, are used for broader ranges. The isothermal compressibility decreases at higher pressures as the bulk modulus increases, reflecting the stiffening of the structure under extreme compression.^[14] Compared to liquid water at the phase transition, Ice VII shows a volume reduction of about 20%, making it roughly 20% denser.^[15] Experimental measurements using diamond anvil cells (DAC) have confirmed densities reaching up to approximately 1.8 g/cm³ at 50 GPa within its stability field up to ~60 GPa at room temperature, demonstrating the phase's ability to sustain significant compression while maintaining its cubic framework.^[16]

Stability and Formation

Pressure-Temperature Stability

Ice VII exhibits thermodynamic stability across an expansive pressure-temperature regime, initiating at approximately 2.1 GPa and 250 K, where it supplants ice VI as the equilibrium phase of water. This boundary marks the transition from the lower-pressure tetragonal structure of ice VI to the cubic body-centered arrangement of ice VII, with the exact transition pressure varying slightly with temperature but consistently around 2–2.5 GPa near room temperature.^[17]^[18] The stability field of ice VII spans to pressures exceeding 150 GPa and temperatures up to approximately 2000 K, encompassing the broadest range among all known molecular ice phases due to its robust body-centered cubic oxygen lattice and inherent structural flexibility. In the water phase diagram, the lower-pressure limit follows the ice VI–ice VII coexistence line, while the high-temperature boundary is defined by the melting curve leading to supercritical fluid or superionic phases; for instance, a triple point occurs near 20 GPa and 875 K involving ice VII, a transitional variant, and the fluid. At ultra-high pressures around 60 GPa, the phase transitions to ice X, characterized by symmetric hydrogen bonding and loss of molecular identity. Atomistic simulations confirm this extensive domain, with ice VII remaining the dominant molecular solid up to 200 GPa below the melting line.^[19]^[20]^[21] Notably, the cubic framework of ice VII persists metastably to at least 128 GPa under static compression, far beyond the equilibrium boundary to ice X, highlighting its kinetic robustness in experimental conditions. The melting curve at modest pressures follows approximately the Simon equation form P = 2.2 + 1.31[(T/365)^{3.3} - 1] (with P in GPa and T in K), illustrating the rise in melting temperature with pressure. The exceptional thermal breadth of this phase arises from elevated configurational entropy due to random proton disorder along the body-centered cubic half-diagonals, which stabilizes the disordered structure against thermal disruption over a wide temperature span.^[22]^[19]

Laboratory Synthesis

Ice VII was first synthesized in the laboratory by Percy W. Bridgman in 1937 using a piston-cylinder apparatus, where liquid water was subjected to static pressures exceeding 2 GPa, marking the initial identification of this high-pressure phase.^[23] This early method relied on mechanical compression within a sealed cylinder to achieve the necessary conditions for phase transition from lower-pressure ice forms or liquid water.^[23] In modern experiments, the primary technique involves compressing ice VI or liquid water in diamond anvil cells (DACs) to pressures above 2 GPa while maintaining controlled temperatures, often using externally heated variants to facilitate single-crystal growth and precise thermodynamic measurements.^[24] These devices enable static compression up to several tens of GPa, allowing researchers to probe the phase's properties under equilibrium conditions.^[25] For rapid, non-equilibrium formation, shock-wave techniques supplement these methods, employing laser-driven or gas-gun dynamic compression to induce phase transitions in microseconds, simulating extreme geophysical processes. Under dynamic compression, Ice VII exhibits rapid nucleation and growth kinetics, with the solidification front propagating at speeds up to 3 km/s, as observed in experiments where entire samples freeze in nanoseconds following transient homogeneous nucleation.^[26] Recent studies have also demonstrated metastable formation of Ice VII from ice VI at room temperature and 1.8 GPa, verified through in situ structural analysis during controlled compression.^[17] Maintaining sample purity during synthesis remains challenging, as unintended phase transitions or inclusions can introduce contaminants such as ice X or lower-pressure polymorphs, necessitating careful control of compression rates and thermal gradients to isolate pure Ice VII.^[17]

Properties

Physical Properties

Ice VII exhibits notable compressibility under high-pressure conditions, characterized by a bulk modulus K_{T0} \approx 21 GPa and a pressure derivative dK/dP \approx 4.5, derived from fits to the high-temperature Birch-Murnaghan equation of state using single-crystal X-ray diffraction data up to 78 GPa and 1000 K.^[27] These parameters reflect the phase's relatively soft response to compression compared to denser high-pressure ices, enabling its stability across a broad pressure range. Sound velocities in Ice VII further illustrate its mechanical behavior, with longitudinal waves propagating at approximately 4.5 km/s and shear waves at about 2.5 km/s near 5 GPa at room temperature, as determined from Brillouin scattering measurements and finite strain analysis of elastic moduli.^[28] Under shear stress at high pressures (3–15 GPa) and elevated temperatures (300–650 K), Ice VII displays plastic deformation through dislocation creep and dynamic recrystallization, evidenced by increased diffraction spots in in situ X-ray diffraction during deformation experiments with strains up to 34%.^[29] This ductile response contrasts sharply with the brittle fracture typical of lower-pressure ice phases like Ice Ih or VI, highlighting Ice VII's enhanced rheological plasticity that influences flow in deep planetary interiors. The thermal expansion coefficient of Ice VII is approximately \alpha \approx 1.4 \times 10^{-4} K^{-1} above 100 K, indicating modest volume changes with temperature under compression.^[30] Hydrogen disorder in the structure contributes to reduced thermal conductivity at higher pressures via phonon scattering from proton tunneling, though this effect is secondary to lattice vibrations.^[31] Optically, Ice VII maintains transparency across the infrared to visible spectrum, facilitating spectroscopic studies under compression. Its refractive index starts at approximately n \approx 1.4 near the phase's lower pressure boundary and increases with density due to closer molecular packing, as measured by interferometric techniques up to 120 GPa.^[32] This pressure-dependent rise in n underscores the phase's evolving dielectric response without significant absorption bands in the probed range.

Electrical Properties

Ice VII displays a high static dielectric constant of approximately 90 at frequencies around 1 GHz, reflecting the orientational polarization of its disordered water molecules, though this value decreases with increasing pressure as the orientational freedom diminishes under compression.^[3] This pressure-induced reduction arises from the constrained proton configurations in the body-centered cubic lattice, limiting dipole alignment.^[33] The dielectric relaxation in Ice VII follows a Debye process dominated by proton reorientation, with a characteristic relaxation time of roughly $10^{-12} s at room temperature.^[3] This dynamics obeys an Arrhenius temperature dependence given by

\tau = \tau_0 \exp\left(\frac{E_a}{kT}\right),

where \tau_0 is the pre-exponential factor, E_a \approx 0.2 eV is the activation energy for reorientation, k is Boltzmann's constant, and T is temperature; the process links to the hydrogen disorder inherent in the structure.^[33] In its insulating molecular phase, Ice VII exhibits very low DC electrical conductivity, \sigma < 10^{-10} S/m, indicative of limited charge carrier mobility, though conductivity rises near pressure-induced transitions due to enhanced proton hopping.^[34] The prospect of ferroelectric behavior in Ice VII remains controversial, stemming from its proton disorder that prevents long-range ordering, with experimental studies confirming no observable net polarization despite theoretical predictions of possible dipole alignment under specific conditions.^[35]^[36] Raman spectroscopy of Ice VII highlights the O-H stretching modes, which exhibit systematic shifts to higher frequencies with increasing pressure, signaling compression of hydrogen bonds and structural stiffening.^[37] These vibrational signatures provide a probe for monitoring phase stability and molecular reorientations.^[38]

Exotic Phases

Superionic Phase

The superionic phase of Ice VII, denoted as SI-bcc, transitions from the standard Ice VII structure at elevated temperatures above approximately 1000–2000 K and pressures greater than 10 GPa, where the oxygen atoms retain a fixed body-centered cubic crystalline lattice while the hydrogen sublattice melts into a mobile, liquid-like state.^[39] This decoupling allows protons to diffuse through the oxygen framework, creating a solid-liquid hybrid with enhanced transport properties distinct from fully molecular or fully ionic phases.^[40] In this regime, the proton diffusion coefficient D_H reaches values around $10^{-4} cm²/s, enabling high ionic conductivity \sigma \approx 10^2 S/m due to the mobile protons acting as charge carriers.^[41] The conductivity follows the relation

\sigma = n q \mu,

where n is the proton number density, q is the proton charge, and \mu is the mobility derived from the Einstein relation \mu = \frac{q D_H}{[k_B](/page/Boltzmann_constant) T}, with k_B the Boltzmann constant and T the temperature; this framework highlights how thermal activation drives the superionic behavior.^[42] Experimental evidence for the superionic phase has been obtained through laser-heated diamond anvil cell (DAC) techniques, where in situ X-ray diffraction and Raman spectroscopy confirm the persistence of the oxygen lattice alongside disordered hydrogen signals indicative of liquid-like motion.^[39] Complementary ab initio molecular dynamics simulations reproduce this asymmetry, showing rapid hydrogen hopping and diffusion while oxygens remain vibrationally confined, validating the phase across a range of terapascal pressures relevant to planetary cores.^[42] A 2025 study employing externally heated DAC experiments up to 42 GPa and 1400 K has revealed an elevated melting boundary and steeper superionic transition, with SI-bcc forming at pressures as low as ~9.5 GPa, lower than prior estimates.^[43] These results suggest broader stability of superionic ice in deep planetary interiors, potentially influencing convective dynamics and magnetic field generation in ice giants like Uranus and Neptune by enhancing electrical and thermal transport.^[43]

Plastic Phase

In February 2025, researchers reported the first experimental observation of plastic ice VII, a dynamic variant of the high-pressure ice VII phase, using quasi-elastic neutron scattering (QENS) measurements conducted at the Institut Laue-Langevin.^[44] This phase had been theoretically predicted over 15 years earlier through molecular dynamics (MD) simulations of classical water models, which suggested its emergence at high pressures above several gigapascals when ice VII is heated or liquid water is cooled.^[45] The experiments confirmed the phase along the high-temperature melting curve of ice VII, at temperatures of 450–600 K and pressures of 3–6 GPa, using a Paris–Edinburgh press to generate the conditions.^[44] Plastic ice VII maintains the body-centered cubic oxygen lattice characteristic of standard ice VII but exhibits orientational disorder where water molecules undergo rapid rotations around their centers of mass, resembling a plastic crystal.^[44] Unlike the superionic phase of ice, which involves translational diffusion of protons, plastic ice VII features arrested translational motion of the molecules while allowing rotational dynamics on picosecond timescales, such as reorientational times of τ₉₀° = 0.51 ± 0.01 ps for 90° jumps at 518 K and 5.5 GPa.^[44] These rotations occur via random jumps between preferential orientations, primarily C₄ (90°) rotations, as validated by complementary MD simulations under matching conditions.^[44] The phase was confirmed through QENS, which revealed quasi-elastic broadening indicative of localized low-energy excitations from hydrogen reorientations, distinct from the frozen dynamics of ordinary ice VII.^[44] Analysis of the scattering data with a single Lorentzian model showed a quasi-elastic peak width that remains nearly constant with wave vector, supporting confined rotational motion rather than free diffusion.^[44] This observation highlights plastic ice VII's potential stability in the 2–10 GPa range at moderate temperatures, filling a gap in water's pressure-temperature phase diagram as an intermediate hybrid between rigid solid and fully liquid states.^[44]

Occurrence

Terrestrial Occurrence

Ice VII has been identified in natural samples from Earth's mantle, primarily as microscopic inclusions trapped within diamonds formed in subduction zones. These inclusions, consisting of aqueous fluids solidified as Ice VII, originate from depths of approximately 400 to 800 km, spanning the upper transition zone and extending into the uppermost lower mantle. The diamonds, which encapsulate the Ice VII during formation, provide direct evidence of free aqueous fluids under extreme pressures of 14 to 25 GPa in water-rich regions of the deep mantle.^[6]^[46] The first confirmed natural occurrences of Ice VII were reported in 2018 from diamonds sourced from the Juina region in Brazil, as well as from cratonic localities including Orapa in Botswana, Shandong in China, and Namaqualand in South Africa. These superdeep diamonds indicate localized saturation of water in the mantle, likely derived from dehydration of subducting oceanic slabs releasing fluids that interact with carbon to precipitate diamond. Such findings highlight Ice VII's role in transporting volatiles like water deep into Earth's interior, influencing mantle dynamics and geochemical cycles despite its overall rarity in sampled materials.^[6]^[47] Ice VII remains stable in lower mantle conditions up to pressures of about 100 GPa, as demonstrated by experimental studies, and may coexist with or form within hydrated silicates in these environments. This stability underscores its potential persistence in cold, water-bearing portions of subducting slabs, facilitating the deep water cycle essential for planetary habitability and tectonic processes.^[6]

Planetary Relevance

Ice VII is a prevalent phase in the mantles of the ice giant planets Uranus and Neptune, where pressures range from 10 to 100 GPa and constitute approximately 50-65% of the planets' total mass, primarily as high-pressure water ice mixed with ammonia and methane.^[48] In these environments, Ice VII transitions into superionic states at higher temperatures (~2000–6000 K), enabling proton diffusion within a stable oxygen lattice.^[49] In water-rich exoplanets, superionic Ice VII emerges as a major structural component in planetary interiors, particularly under conditions exceeding 50 GPa and 1500–2000 K, where its high ionic conductivity (10–120 S cm⁻¹) facilitates the generation of magnetic fields through dynamo action in convective layers.^[50] This conductivity arises from mobile hydrogen ions in body-centered cubic or face-centered cubic oxygen lattices, distinguishing it from conventional insulators and influencing the overall electromagnetic properties of these worlds.^[50] Planetary models of hot Neptunes incorporate layers of Ice VII in their deep interiors to account for enhanced heat transport mechanisms, where the phase's stability permits convective electrolyte permeation through permeable high-pressure ice mantles, affecting thermal evolution and atmospheric dynamics.^[51] Recent 2025 studies have revealed X-ray diffraction signatures of the superionic transition in face-centered cubic water ice under warm dense conditions, showing a remarkable thermal volume expansion associated with the phase change and implications for material structures in planetary interiors.^[52] Additionally, ab initio simulations indicate that the superionic phase of ice VII forms at lower pressures around 9.5 GPa and temperatures up to 1400 K, as confirmed by experiments up to 42 GPa, influencing models of water-rich exoplanet interiors and deep mantle dynamics in Earth-like bodies.^[43] Indirect observational evidence for water-bearing exoplanets, potentially hosting Ice VII in their interiors, comes from Hubble and JWST transmission spectra revealing water vapor in atmospheres of sub-Neptune-sized worlds, such as GJ 9827 d and others, implying substantial subsurface water inventories.^[53]

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Observation of plastic ice VII by quasi-elastic neutron scattering
Feb 12, 2025 · In ice VII, the oxygen atoms form a body-centred cubic structure where each oxygen atom connects to four hydrogen atoms through two covalent and ...
[44]
A plastic phase of water from computer simulation - AIP Publishing
May 23, 2008 · Molecular dynamics simulations of three models of water demonstrate that a plastic ice phase appears when ice VII is heated or liquid water ...
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Coupled deep-mantle carbon-water cycle: Evidence from lower ...
May 28, 2021 · Huang, E. Greenberg, et al. Ice-VII inclusions in diamonds: evidence for aqueous fluid in Earth's deep mantle. Science, 359 (2018) ...
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[PDF] Diamonds Help Solve the Enigma of Earth's Deep Water - GIA
So-called superdeep diamonds form at depths greater than 200 km in areas of the mantle ... (2018) Ice-VII inclusions in diamonds: Evidence for aqueous fluid in ...
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Uranus and Neptune: Origin, Evolution and Internal Structure
Mar 25, 2020 · Uranus and Neptune have masses of about 14.5 and 17 (Earth mass), respectively. Their sizes are about four times that of the Earth, and they are ...
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Double superionicity in icy compounds at planetary interior conditions
Nov 21, 2023 · At the high pressures (~10–700 GPa) and temperatures (~2000–6000 K) of Uranus and Neptune, water and ammonia exhibit superionic states, in which ...
[49]
The phase diagram of high-pressure superionic ice - Nature
Aug 28, 2015 · Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets.
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Stability of high-temperature salty ice suggests electrolyte ... - Nature
Jun 21, 2022 · Increasing the temperature in ice VII activates a dynamic orientational disorder of the H2O molecules. Increasing both pressure and temperature ...
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X-Ray Signature of the Superionic Transition in Warm Dense fcc ...
Feb 21, 2025 · Ice VII exhibits the simplest high density packing ... The superionic properties of ice could strongly impact planetary interior modeling
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NASA's Hubble Finds Water Vapor in Small Exoplanet's Atmosphere
Jan 25, 2024 · Astronomers using NASA's Hubble Space Telescope have observed water vapor in the atmosphere of the smallest exoplanet ever detected.Missing: VII evidence