Ice II is a

rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...

crystalline form of

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaqu ...

with a highly ordered structure. It is formed from ice I_h by compressing it at a temperature of 198 K at 300

MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mou ...

or by decompressing

ice V Ice V, pronounced "ice five", is a monoclinic crystalline phase of water, formed by cooling water to 253 K at 500 MPa. It has a density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The s ...

. When heated it undergoes transformation to

ice III Ice III is a form of solid matter which consists of tetragonal crystalline ice, formed by cooling water down to at . It is the least dense of the high-pressure water phases, with a density of (at 350 MPa). It has a very high relative permitti ...

. Ordinary

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

ice is known as ice I_h, (in the Bridgman nomenclature). Different types of ice, from ice II to

ice XIX Ice XIX is a proposed crystalline phase of water. Along with ice XV, it is one of two phases of ice directly related to ice VI. Ice XIX is prepared by cooling HCl-doped ice VI at a pressure above 1.6 GPa down to about 100 K. As of 2022, its cry ...

, have been created in the laboratory at different temperatures and pressures. It is thought that the cores of

icy moon Icy commonly refers to conditions involving ice, a frozen state, usually referring to frozen water. Icy or Icey may also refer to: People * Icy Spicy Leoncie, an Icelandic-Indian musician Arts, entertainment, and media Music * ICY (band), a voca ...

s like Jupiter's Ganymede may be made of ice II.

History

The properties of ice II were first described and recorded by

Gustav Heinrich Johann Apollon Tammann Gustav Heinrich Johann Apollon Tammann ( – 17 December 1938) was a prominent Baltic German chemist-physicist who made important contributions in the fields of glassy and solid solutions, heterogeneous equilibria, crystallization, and metallurg ...

in 1900 during his experiments with ice under high pressure and low temperatures. Having produced ice III, Tammann then tried condensing the ice at a temperature between under of pressure. Tammann noted that in this state ice II was denser than he had observed ice III to be. He also found that both types of ice can be kept at normal

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

in a stable condition so long as the temperature is kept at that of

liquid air Liquid air is air that has been cooled to very low temperatures ( cryogenic temperatures), so that it has condensed into a pale blue mobile liquid. To thermally insulate it from room temperature, it is stored in specialized containers ( vacuum in ...

, which slows the change in conformation back to ice I_h. In later experiments by Bridgman in 1912, it was shown that the difference in volume between ice II and ice III was in the range of . This difference hadn't been discovered by Tammann due to the small change and was why he had been unable to determine an equilibrium curve between the two. The curve showed that the structural change from ice III to ice II was more likely to happen if the medium had previously been in the structural conformation of ice II. However, if a sample of ice III that had never been in the ice II state was obtained, it could be supercooled even below −70 °C without it changing into ice II. Conversely, however, any superheating of ice II was not possible in regards to retaining the same form. Bridgman found that the equilibrium curve between ice II and

ice IV Ice IV is a metastable high-pressure phase of ice. It is formed when liquid water is compressed with an immense force. Preparation Several organic nucleating reagents had been proposed to selectively crystallize ice IV from liquid water, but e ...

was much the same as with ice III, having the same stability properties and small volume change. The curve between ice II and

was extremely different, however, with the curve's bubble being essentially a straight line and the volume difference being almost always .

Quest for a hydrogen-disordered counterpart of ice II

As ice II is completely hydrogen ordered, the presence of its disordered counterpart is a great matter of interest. Shephard et al. investigated the phase boundaries of NH₄F-doped ices because NH₄F has been reported to be a hydrogen disordering reagent. However, adding 2.5 mol% of NH₄F resulted in the disappearance of ice II instead of the formation of a disordered ice II. According to the DFC calculation by Nakamura et al. , the phase boundary between ice II and its disordered counterpart is estimated to be in the stability region of liquid water.

References

Water ice {{inorganic-compound-stub

History

Quest for a hydrogen-disordered counterpart of ice II

See also

References