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This article is about water ice. For the broader concept of "ices" as used in the planetary sciences, see . For other uses, see .
Frozen water in the form of an ordinary household ice cube. The white zone in the center is the result of tiny air bubbles.
by , 1902. Snow is ice that grows from water vapor in Earth's , which is why it usually displays crystal shapes.
into a solid state. Depending on the presence of
such as particles of soil or bubbles of air, it can appear transparent or a more or less
bluish-white color.
In the , ice is abundant and occurs naturally from as close to the Sun as
to as far as away the
objects. Beyond the Solar System, it occurs as . It is abundant on 's surface – particularly
and above the  – and, as a common form of
and , plays a key role in Earth's
and . It falls as snowflakes and hail or occurs as frost, icicles or .
can exhibit up to sixteen different
() that depend on temperature and pressure. When water is cooled rapidly (quenching), up to three different types of
can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below 20 K giving rise to . Virtually all the ice on Earth's surface and in its atmosphere is of a
denoted as
(spoken as "ice one h") with minute traces of cubic ice denoted as . The most common
to ice Ih occurs when liquid water is cooled below 0 (273.15, 32) at . It may also be
directly by , as happens in the formation of frost. The transition from ice to water is melting and from ice directly to water vapor is .
Ice is used in a variety of ways, including cooling,
The three-dimensional crystal structure of H2O ice Ih (c) is composed of bases of H2O ice molecules (b) located on lattice points within the two-dimensional hexagonal space lattice (a). The values for the H–O–H angle and O–H distance have come from Physics of Ice with uncertainties of ±1.5° and ±0.005 ?, respectively. The white box in (c) is the unit cell defined by Bernal and Fowler.
As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a .[] It possesses a regular
structure based on the
of water, which consists of a single
bonded to two , or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of
between adjacent oxyge while it is a weak bond, it is nonetheless critical in controlling the structure of both water and ice.
An unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8.3% less dense than liquid water. The
of ice is 0.9167 g/cm3 at 0 °C, whereas water has a density of 0.9998 g/cm? at the same temperature. Liquid water is densest, essentially 1.00 g/cm?, at 4 °C and becomes less dense as the water molecules begin to form the
as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm? at -180 °C (93 K).
When water freezes, it increases in volume (about 9% for fresh water). The effect of expansion during freezing can be dramatic, and ice expansion is a basic cause of
weathering of rock in nature and damage to building foundations and roadways from . It is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes.
The result of this process is that ice (in its most common form) floats on liquid water, which is an important feature in Earth's . It has been argued that without this property, natural bodies of water would freeze, in some cases permanently, from the bottom up, resulting in a loss of bottom-dependent animal and plant life in fresh and sea water. Sufficiently thin
allow light to pass through while protecting the underside from short-term weather extremes such as . This creates a sheltered environment for bacterial and algal colonies. When sea water freezes, the ice is riddled with brine-filled channels which sustain
such as bacteria, algae, copepods and annelids, which in turn provide food for animals such as krill and specialised fish like the , fed upon in turn by larger animals such as
When ice melts, it absorbs as much
as it would take to heat an equivalent mass of water by 80 °C. During the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the hydrogen bonds between ice (water) molecules. Energy becomes available to increase the thermal energy (temperature) only after enough hydrogen bonds are broken that the ice can be considered liquid water. The amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the .
As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of an oxygen–hydrogen (O–H) bond stretch. Compared with water, this absorption is shifted toward slightly lower energies. Thus, ice appears blue, with a slightly greener tint than for liquid water. Since absorption is cumulative, the color effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path through the ice.
Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color rather than the ice itself. For instance,
containing impurities (e.g., sediments, algae, air bubbles) can appear brown, grey or green.
Frozen waterfall in southeast New York
Ice was originally thought to be slippery due to the pressure of an object coming into contact with the ice, melting a thin layer of the ice and allowing the object to glide across the surface. For example, the blade of an ice skate, upon exerting pressure on the ice, would melt a thin layer, providing lubrication between the ice and the blade. This explanation, called "pressure melting", originated in the 19th century. It, however, did not account for skating on ice temperatures lower than -4.0 °C, which is often skated upon.
Another, equally old explanation, is that ice is slippery because ice molecules at the interface cannot properly bond with the molecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These molecules remain in a semi-liquid state, providing lubrication regardless of pressure against the ice exerted by any object. However, the significance of this hypothesis is disputed by experiments showing a high
for ice using .
In the 20th century, a further explanation, called "friction heating", was proposed, whereby friction of the material is the cause of the ice layer melting. However, this theory does not sufficiently explain why ice is slippery when standing still even at below-zero temperatures.
More recently, a comprehensive theory of ice friction, which takes into account all the above-mentioned friction mechanisms, has been presented. This model allows quantitative estimation of the friction coefficient of ice against various materials as a function of temperature and sliding speed. In typical conditions related to winter sports and tires of a vehicle on ice, melting of a thin ice layer due to the frictional heating is the primary reason for the slipperiness.
Feather ice on the plateau near . The crystals form at temperatures below -30 °C (-22 °F).
The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the . Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and
are an important storage mecha over time, they may sublimate or melt.
is an important source of seasonal fresh water. The
defines several kinds of ice depending on origin, size, shape, influence and so on.
are forms of ice that contain gas molecules trapped within its crystal lattice.
Main article:
Ice that is found at sea may be in the form of
floating in the water,
fixed to a shoreline or
if attached to the sea bottom. Ice which
(breaks off) from an
or glacier may become an ice berg. Sea ice can be forced together by currents and winds to form
up to 12 metres (39 ft) tall. Navigation through areas of sea ice occurs in openings called "" or "" or requires the use of a special ship called an "".
Ice on deciduous tree after
Ice on land ranges from the largest type called an "" to smaller
to glaciers and
is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen layer. This water then freezes, causing the water table to rise further and repeat the cycle. The result is a stratified ice deposit, often several meters thick.
is a type of winter storm called an
where rain falls and then freezes producing a
of ice. Ice can also form icicles, similar to
in appearance, or -like forms as water drips and re-freezes.
The term "ice dam" has three meanings (others discussed below). On structures, an
is the buildup of ice on a sloped roof which stops melt water from draining properly and can cause damage from water leaks in buildings.
A small frozen
Ice which forms on moving water tends to be less uniform and stable than ice which forms on calm water.
(sometimes called "ice dams"), when broken chunks of ice pile up, are the greatest ice hazard on rivers. Ice jams can cause flooding, damage structures in or near the river, and damage vessels on the river. Ice jams can cause some
industrial facilities to completely shut down. An ice dam is a blockage from the movement of a glacier which may produce a . Heavy ice flows in rivers can also damage vessels and require the use of an icebreaker to keep navigation possible.
are circular formations of ice surrounded by water in a river.
is a formation of ice generally created in areas with less calm conditions.
Ice forms on calm water from the shores, a thin layer spreading across the surface, and then downward. Ice on lakes is generally four types: Primary, secondary, superimposed and agglomerate. Primary ice forms first. Secondary ice forms below the primary ice in a direction parallel to the direction of the heat flow. Superimposed ice forms on top of the ice surface from rain or water which seeps up through cracks in the ice which often settles when loaded with snow.
occurs when floating pieces of ice are driven by the wind piling up on the windward shore.
is a form of
that develops in columns perpendicular to the surface of a lake.
Ice formation on vehicle windshield
Rime is a type of ice formed on cold objects when drops of water crystallize on them. This can be observed in
weather, when the temperature drops during the night.
contains a high proportion of trapped air, making it appear white rather than transparent, and giving it a density about one quarter of that of pure ice.
is comparatively dense.
Main article:
An accumulation of ice pellets
are a form of precipitation consisting of small,
balls of ice. This form of precipitation is also referred to as "sleet" by the United States . (In
"sleet" refers to ). Ice pellets are usually smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with . The
code for ice pellets is PL.
Ice pellets form when a layer of above-freezing air is located between 1,500 and 3,000 metres (4,900 and 9,800 ft) above the ground, with sub-freezing air both above and below it. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A temperature profile showing a warm layer above the ground is most likely to be found in advance of a
during the cold season, but can occasionally be found behind a passing .
Main article:
A large hailstone, about 6 cm (2.4 in) in diameter
Like other precipitation, hail forms in storm
water droplets freeze on contact with , such as
or . The storm's
blows the hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted up again. Hail has a diameter of 5 millimetres (0.20 in) or more. Within
code, GR is used to indicate larger hail, of a diameter of at least 6.4 millimetres (0.25 in) and GS for smaller. Stones just larger than -sized are one of the most frequently reported hail sizes. Hailstones can grow to 15 centimetres (6 in) and weigh more than 0.5 kilograms (1.1 lb). In large hailstones,
released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud.
Hail forms in strong
clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 °C (32 °F). Hail-producing clouds are often identifiable by their green coloration. The growth rate is maximized at about -13 °C (9 °F), and becomes vanishingly small much below -30 °C (-22 °F) as supercooled water droplets become rare. For this reason, hail is most common within continental interiors of the mid-latitudes, as hail formation is considerably more likely when the freezing level is below the altitude of 11,000 feet (3,400 m).
of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporational cooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. Accordingly, hail is actually less common in the tropics despite a much higher frequency of thunderstorms than in the mid-latitudes because the
over the tropics tends to be warmer over a much greater depth. Hail in the tropics occurs mainly at higher elevations.
Main article:
Snowflake viewed in an optical microscope
Snow crystals form when tiny
cloud droplets (about 10
in diameter) . These droplets are able to remain liquid at temperatures lower than -18 °C (255 K; 0 °F), because to freeze, a few molecules in the droplet need to get together by chance to form an arrangement similar to th then the droplet freezes around this "nucleus." Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than -35 °C (238 K; -31 °F). In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Our understanding of what particles make efficient ice nuclei is poor – what we do know is they are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei are used in . The droplet then grows by condensation of water vapor onto the ice surfaces.
Main article:
So-called "diamond dust", also known as ice needles or ice crystals, forms at temperatures approaching -40 °C (-40 °F) due to air with slightly higher moisture from aloft mixing with colder, surface-based air. The METAR identifier for diamond dust within international hourly weather reports is IC.
Harvesting ice on
in , c. 1905
B&W film of 1919 ice harvest at Pocono Manor in the
An ice manufacturing plant in , India
Ice is now mechanically produced on a large scale, but before
was developed ice was harvested from natural sources for human use.
Main article:
Ice-harvesting exhibit at
Once harvested, ice was transported in wagons, such as this one, restored in 1965 and displayed at the
Ice has long been valued as a means of cooling. In 400 BC Iran,
engineers had already mastered the technique of storing ice in the middle of summer in the desert. The ice was brought in during the winters from nearby mountains in bulk amounts, and stored in specially designed, naturally cooled refrigerators, called
(meaning ice storage). This was a large underground space (up to 5000 m?) that had thick walls (at least two meters at the base) made of a special mortar called , composed of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, and which was known to be resistant to heat transfer. This mixture was thought to be completely water impenetrable. The space often had access to a , and often contained a system of
which could easily bring temperatures inside the space down to frigid levels on summer days. The ice was used to chill treats for royalty.
There were thriving industries in 16th/17th century England whereby low-lying areas along the
were flooded during the winter, and ice harvested in carts and stored inter-seasonally in insulated wooden houses as a provision to an icehouse often located in large country houses, and widely used to keep fish fresh when caught in distant waters. This was allegedly copied by an Englishman who had seen the same activity in China. Ice was imported into England from Norway on a considerable scale as early as 1823.
In the United States, the first cargo of ice was sent from New York City to
in 1799, and by the first half of the 19th century, ice harvesting had become big business. , who became known as the "Ice King", worked on developing better insulation products for the long distance shipment of ice, espec this became known as the .
sent ice to , , Switzerland sent it to F and Germany sometimes was supplied from
lakes. The
building used ice harvested in the winter from
for air conditioning.
were used to store ice formed in the winter, to make ice available all year long, and early
were known as , because they had a block of ice in them. In many cities, it was not unusual to have a regular ice
service during the summer. The advent of artificial refrigeration technology has since made delivery of ice obsolete.
Ice is still harvested for . For example, a
is used to get ice for the
each year from the frozen surface of the .
Ice is now produced on an industrial scale, for uses including food storage and processing, chemical manufacturing, concrete mixing and curing, and consumer or packaged ice. Most commercial
produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques. Large batch ice makers can produce up to 75 tons of ice per day.
Ice production in 2002, there were 426 commercial ice-making companies in the United States, with a combined value of shipments of $595,487,000.
For small-scale ice production, many modern home refrigerators can also make ice with a built in , which will typically make
or crushed ice. Stand-alone icemaker units that make ice cubes are often called ice machines.
Small Lake
Main article:
Ice also plays a central role in winter recreation and in many sports such as , , , , , , ,
and sled racing on ,
and . Many of the different sports played on ice get international attention every four years during the .
A sort of sailboat on blades gives rise to . Another sport is , where drivers must speed on lake ice, while also controlling the skid of their vehicle (similar in some ways to ). The sport has even been modified for .
Ice cubes or
can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near 0 °C (32 °F).
Ice can be used to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.
Ice pier during 1983 cargo operations. , Antarctica
Engineers used the formidable strength of pack ice when they constructed Antarctica's first floating
in 1973. Such ice piers are used during cargo operations to load and offload ships. Fleet operations personnel make the floating pier during the winter. They build upon naturally occurring frozen seawater in
until the dock reaches a depth of about 22 feet (6.7 m). Ice piers have a lifespan of three to five years.
Structures and ice sculptures are built out of large chunks of ice or by spraying water The structures are mostly ornamental (as in the case with ), and not practical for long-term habitation.
exist on a seasonal basis in a few cold areas.
are another example of a temporary structure, made primarily from snow.
In cold climates, roads are regularly prepared on floating ice of lakes and archipelago areas. Temporarily, even a railroad has been built on ice.
During World War II,
was an Allied programme which investigated the use of
(wood fibers mixed with ice) as a possible material for warships, especially aircraft carriers, due to the ease with which a vessel immune to torpedoes, and a large deck, could be constructed by ice. A small-scale prototype was built, but the need for such a vessel in the war was removed prior to building it in full-scale.
Ice can be used to start a fire by carving it into a lens which will focus sunlight onto kindling. A fire will eventually start.
Ice has even been used as the material for a variety of musical instruments, for example by percussionist .
Ice was once used to cool refrigerators in the 19th century, called "."
Ice can be used as part of an , using battery- or
fans to blow hot air over the ice. This is especially useful during
when power is out and standard (electrically powered) air conditioners do not work.
U.S. Coast Guard
near , February 2002
Ice can for
near the , being ice-free is an ideally, all year long. Examples are
(Russia, formerly Finland) and
(Norway). Harbors which are not ice-free are opened up using .
Ice forming on
is a dangerous winter hazard.
is very difficult to see, because it lacks the expected frosty surface. Whenever there is freezing rain or snow which occurs at a temperature near the melting point, it is common for ice to build up on the
of vehicles. Driving safely requires the removal of the ice build-up.
are tools designed to break the ice free and clear the windows, though removing the ice can be a long and laborious process.
Far enough below the freezing point, a thin layer of ice crystals can form on the inside surface of windows. This usually happens when a vehicle has been left alone after being driven for a while, but can happen while driving, if the outside temperature is low enough. Moisture from the driver's breath is the source of water for the crystals. It is troublesome to remove this form of ice, so people often open their windows slightly when the vehicle is parked in order to let the moisture dissipate, and it is now common for cars to have rear-window
to solve the problem. A similar problem can happen in homes, which is one reason why many colder regions require
for insulation.
When the outdoor temperature stays below freezing for extended periods, very thick layers of ice can form on
and other bodies of water, although places with flowing water require much colder temperatures. The ice can become thick enough to drive onto with
and . Doing this safely requires a thickness of at least 30 cm (one foot).
For ships, ice presents two distinct hazards. Spray and freezing rain can produce an ice build-up on the superstructure of a vessel sufficient to make it unstable, and to require it to be hacked off or melted with steam hoses. And icebergs – large masses of ice floating in water (typically created when
reach the sea) – can be dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, the most famous probably being the .
Ice formation on window glass of high altitude flying airplane
For aircraft, ice can cause a number of dangers. As an aircraft climbs, it passes through air layers of different temperature and humidity, some of which may be conducive to ice formation. If ice forms on the wings or control surfaces, this may adversely affect the flying qualities of the aircraft. During the , the British aviators Captain
and Lieutenant
encountered such icing conditions – Brown left the cockpit and climbed onto the wing several times to remove ice which was covering the engine air intakes of the
aircraft they were flying.
A particular icing vulnerability associated with reciprocating internal combustion engines is the . As air is sucked through the carburetor into the engine, the local air pressure is lowered, which causes
cooling. So, in humid near-freezing conditions, the carburetor will be colder, and tend to ice up. This will block the supply of air to the engine, and cause it to fail. For this reason, aircraft reciprocating engines with carburetors are provided with . The increasing use of —which does not require carburetors—has made "carb icing" less of an issue for reciprocating engines.
Jet engines do not experience carb icing, but recent evidence indicates that they can be slowed, stopped, or damaged by internal icing in certain types of atmospheric conditions much more easily than previously believed. In most cases, the engines can be quickly restarted and flights are not endangered, but research continues to determine the exact conditions which produce this type of icing, and find the best methods to prevent, or reverse it, in flight.
"Ice IV" redirects here. For the high speed train, see .
"Ice X" redirects here. For other uses, see .
Pressure dependence of ice melting
Ice may be any one of the 17 known solid crystalline phases of , or in an amorphous solid state at various densities.
Most liquids under increased pressure freeze at higher temperatures because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: For some pressures higher than 1 atm (0.10 MPa), water freezes at a temperature below 0 °C, as shown in the phase diagram below. The melting of ice under high pressures is thought to contribute to the movement of glaciers.
Ice, water, and
can coexist at the , which is exactly 273.16 K (0.01 °C) at a pressure of 611.657 . The
is in fact defined as 1/273.16 of the difference between this triple point and . Unlike most other solids, ice is difficult to . In an experiment, ice at -3 °C was superheated to about 17 °C for about 250 picoseconds.
Subjected to higher pressures and varying temperatures, ice can form in 16 separate known phases. With care, all these phases except ice X can be recovered at ambient pressure and low temperature in metastable form. The types are differentiated by their crystalline structure, proton ordering and density. There are also two
phases of ice under pressure, both fully hydrogen- these are
and . Ice XII was discovered in 1996. In 2006,
were discovered. Ices , XIII, and XIV are hydrogen-ordered forms of ices Ih, V, and XII respectively. In 2009, ice XV was found at extremely high pressures and -143 °C. At even higher pressures, ice is pr this has been variously estimated to occur at 1.55 TPa or 5.62 TPa.
As well as crystalline forms, solid water can exist in amorphous states as
(ASW) of varying densities. Water in the
is dominated by amorphous ice, making it likely the most common form of water in the universe. Low-density ASW (LDA), also known as hyperquenched glassy water, may be responsible for
on Earth and is usually formed by
of water vapor in cold or vacuum conditions. High-density ASW (HDA) is formed by compression of ordinary ice Ih or LDA at GPa pressures. Very-high-density ASW (VHDA) is HDA slightly warmed to 160K under 1–2 GPa pressures.
In outer space, hexagonal crystalline ice (the predominant form found on Earth) is extremely rare. Amorphou however, hexagonal crystalline ice can be formed by volcanic action.
pressure-temperature
of water. The
correspond to some ice phases listed below.
Characteristics
ice is an ice lacking crystal structure. Amorphous ice exists in three forms: low-density (LDA) formed at atmospheric pressure, or below, high density (HDA) and very high density amorphous ice (VHDA), forming at higher pressures. LDA forms by extremely quick cooling of liquid water ("hyperquenched glassy water", HGW), by depositing water vapour on very cold substrates ("amorphous solid water", ASW) or by heating high density forms of ice at ambient pressure ("LDA").
Normal hexagonal crystalline ice. Virtually all ice in the
is ice Ih, with the exception only of a small amount of ice Ic.
A metastable
crystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It is produced at temperatures between 130 and 220 K, and can exist up to 240 K, when it transforms into ice Ih. It may occasionally be present in the upper atmosphere.
crystalline form with highly ordered structure. Formed from ice Ih by compressing it at temperature of 190–210 K. When heated, it undergoes transformation to ice III.
crystalline ice, formed by cooling water down to 250 K at 300 MPa. Least dense of the high-pressure phases. Denser than water.
A metastable rhombohedral phase. It can be formed by heating
slowly at a pressure of 810 MPa. It doesn't form easily without a nucleating agent.
crystalline phase. Formed by cooling water to 253 K at 500 MPa. Most complicated structure of all the phases.
A tetragonal crystalline phase. Formed by cooling water to 270 K at 1.1 GPa. Exhibits .
A cubic phase. The hydrogen atoms' positions are disordered. Exhibits Debye relaxation. The hydrogen bonds form two interpenetrating lattices.
A more ordered version of ice VII, where the hydrogen atoms assume fixed positions. It is formed from ice VII, by cooling it below 5 °C (278 K).
A tetragonal phase. Formed gradually from ice III by cooling it from 208 K to 165 K, stable below 140 K and pressures between 200 MPa and 400 MPa. It has density of 1.16 g/cm3, slightly higher than ordinary ice.
Proton-ordered symmetric ice. Forms at about 70 GPa.
An , low-temperature equilibrium form of hexagonal ice. It is . Ice XI is considered the most stable configuration of ice Ih. The natural transformation process is very slow and ice XI has been found in Antarctic ice 100 to 10,000 years old. That study indicated that the temperature below which ice XI forms is -36 °C (240 K).
A tetragonal, metastable, dense crystalline phase. It is observed in the phase space of ice V and ice VI. It can be prepared by heating high-density amorphous ice from 77 K to about 183 K at 810 MPa. It has a density of 1.3 g cm-3 at 127 K (i.e., approximately 1.3 times more dense than water).
A monoclinic crystalline phase. Formed by cooling water to below 130 K at 500 MPa. The proton-ordered form of ice V.
An orthorhombic crystalline phase. Formed below 118 K at 1.2 GPa. The proton-ordered form of ice XII.
The proton-ordered form of ice VI formed by cooling water to around 80–108 K at 1.1 GPa.
The least dense crystalline form of water, topologically equivalent to the empty structure of sII .
An alternative formulation of the phase diagram for certain ices and other phases of water
Main article:
The solid phases of several other volatile substances are also referred to as ices; generally a volatile is classed as an ice if its melting point lies above or around 100 K. The best known example is , the solid form of .
A "magnetic analogue" of ice is also realized in some insulating magnetic materials in which the magnetic moments mimic the position of protons in water ice and obey energetic constraints similar to the Bernal-Fowler
arising from the
of the proton configuration in water ice. These materials are called .
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