Everyday ice is a crystal, which means its molecules are lined up in a repeating pattern. Amorphous ice is an amorphous solid form of water, meaning it consists of water molecules that are randomly arranged like the atoms of common glass. Amorphous ice is produced by cooling liquid water very quickly (around 1,000,000 K/s), so the molecules don't have enough time to form a crystal lattice. To meet Wikipedias quality standards, this article or section may require cleanup. ... Quartz crystal In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ... Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ... Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... The ordinary meaning of lattice is the basis for several technical usages A cherry lattice pastry A mathematical lattice that is a type of partially ordered set. ...

Just as there are many different crystalline forms of ice (currently fourteen), there are also different forms of amorphous ice, distinguished principally by their densities. Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Density (symbol: ρ - Greek: rho) is a measure of mass per volume. ...

Formation techniques

The key to producing amorphous ice is the rate of cooling. The liquid water must be cooled to its glass transition temperature (about 136 K) in a matter of milliseconds to prevent the spontaneous formation of crystals. This is analogous to the production of ice cream, which must also be frozen quickly to prevent the growth of crystals and guarantee a smooth texture. The difference is that pure water forms crystals much more readily than the heterogeneous mixture of ingredients in ice cream, so amorphous water is more difficult to produce, requiring a physics lab rather than an ice cream churn. A material’s glass transition temperature, Tg, is the temperature below which molecules have little relative mobility. ... Missing image Ice cream is often served on a stick Boxes of ice cream are often found in stores in a display freezer. ...

Pressure is another important factor in the formation of amorphous ice, and changes in pressure may cause one form to convert into another. The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ...

Chemicals known as cryoprotectants can be added to water, to lower its freezing point (like an antifreeze) and increase viscosity, which inhibits formation of crystals. Vitrification without addition of cryoprotectants can be achieved by very rapid cooling. These techniques are used in biology for cryopreservation of cells and tissues. A cryoprotectant is a substance that is used to protect biological tissue from freezing damage (damage due to ice formation). ... A man pouring antifreeze into his vehicle. ... A vitrification experiment for the study of nuclear waste disposal at Pacific Northwest National Labs. ... Cryopreservation of plant shoots. ...

Forms

Low-density amorphous ice

Low-density amorphous ice, also called LDA, vapor-deposited amorphous water ice, amorphous solid water (ASW) or hyperquenched glassy water (HGW), is usually formed in the laboratory by a slow accumulation of water vapor molecules (physical vapor deposition) onto a very smooth metal crystal surface under 120 K. In outer space it is expected to be formed in a similar manner on a variety of cold substrates, such as dust particles. It is expected to be common in the subsurface of exterior planets and comets.^[1] Physical vapor deposition (PVD) is a technique used to deposit thin films of various materials onto various surfaces (e. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. ... Layers of Atmosphere - not to scale (NOAA) Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ...

Melting past its glass transition temperature (T_g) between 120 and 140 K, LDA is more viscous than normal water. Recent studies have shown the viscous liquid stays in this alternative form of liquid water up to somewhere between 140 and 210 K, a temperature range that is also inhabited by ice I_c^[2]. LDA has a density of 0.94 g/cm³, less dense than the densest water (1.00 g/cm³ at 277 K), but denser than ordinary ice (ice I_h). Viscosity is a measure of the resistance of a fluid to deformation under shear stress. ... Ice Ih is the hexagonal crystal form of ordinary ice, or frozen water. ...

Hyperquenched glassy water (HGW) is formed by spraying a fine mist of water droplets into a liquid such as propane around 80 K or by hyperquenching fine micrometer-sized droplets on a sample-holder kept at liquid nitrogen temperature in a vacuum. Cooling rates above 10⁴ K/sec are required to prevent crystallization of the droplets. At liquid nitrogen temperature HGW is kinetically stable and can be stored for many years.

High-density amorphous ice

High-density amorphous ice (HDA) can be formed by compressing ice Ih at temperatures below ~140K. At 77 K, HDA forms from ordinary natural ice at around 1.6 GPa^[3] and from LDA at around 0.5 GPa^[4] (atmospheric pressure at sea level is about 0.1 MPa), and has a density of 1.17 g/cm³ when recovered back to ambient pressure. The resulting collapsed structure resists reverting to LDA at lower pressures and is stable for months at 77 K and 0.1 MPa.

Very-high-density amorphous ice

Very-high-density amorphous ice (VHDA), discovered in 2001 at the University of Innsbruck,^[5] is usually made from high-density amorphous ice at 77 K by heating it up to about 160 K while under pressures of ca. 1-2 GPa to create an annealing process. It has a density of 1.26 g/cm³. Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. ...

Uses

Amorphous ice is used in some scientific experiments, especially in electron cryomicroscopy of biomolecules.^[6] The individual molecules can be preserved for imaging in a state close to what they are in liquid water. Electron cryomicroscopy is a form of electron microscopy (EM) where the sample is studied at cryo temperatures (generally liquid nitrogen temperatures). ...

References

1. ^ Estimation of water-glass transition temperature based on hyperquenched glassy water experiments from Science (requires registration).
2. ^ Liquid water in the domain of cubic crystalline ice I_c from AIP.
3. ^ O. Mishima and LD Calvert, and E. Whalley, Nature 310, 393 (1984)
4. ^ O. Mishima, LD Calvert, and E. Whalley, Nature 314, 76 (1985).
5. ^ Loerting, T., Salzmann, C., Kohl, I., Mayer, E., Hallbrucker, A., A 2nd distinct structural state of HDA at 77 K and 1 bar, PhysChemChemPhys 3:5355-5357. (2001).
6. ^ Dubochet, J., M. Adrian, J. J. Chang, J. C. Homo, J. Lepault, A. W. McDowell, and P. Schultz. Cryo-electron microscopy of vitrified specimens. Q. Rev. Biophys. 21:129-228. (1988).

Science is the journal of the American Association for the Advancement of Science (AAAS). ... The American Institute of Physics (AIP) is a professional body representing American physicists and publishing physics related journals. ...

External links

• Discussion of amorphous ice at LSBU's website.
• Journal of Physics article
• Glass transition in hyperquenched water from Nature (requires registration)
• Glassy Water from Science, on phase diagrams of water (requires registration)
• AIP accounting discovery of VHDA
• HDA in space
• Computerized illustrations of molecular structure of HDA
• Structure of amorphous ice