Ice VII is a cubic shape of ice crystals. This can be formed from liquid water over 3 GPa (30,000 atmospheres) by lowering the temperature to room temperature, or by decompressing heavy water (D 2 O) ice VI below 95 K. Normal water ice is known as my ice h , (in the Bridgman nomenclature). Various types of ice, from ice II to XVI ice, have been made in the laboratory at different temperatures and pressures. Ice VII is metastable over various temperatures and pressures and turned into low-density amorphous ice (LDA) above 120 Â ° K (-153 Â ° C). Ice VII has a triple point with liquid water and VI ice at 355 K and 2,216 GPa, with a melting line extending to at least 715 Â ° C (442 Â ° C) and 10 GPa. Ice VII can be formed in a nanosecond with rapid compression through shock waves. This can also be made by increasing the pressure on the VI ice at room temperature.
Like most ice phases (including ice I h ), the hydrogen atom positions are irregular. In addition, oxygen atoms are not regular at some sites. The ice structure VII consists of a hydrogen bonding framework in the form of two interpenetrating (but non-bound) sublattices. The hydrogen bond passes through the center of the water hexamers and thus does not connect the two lattices. Ice VII has a density of about 1.65 g cm -3 (at 2.5 GPa and 25 Â ° C (77 Â ° F; 298 Â ° K)), which is less than twice the ice density cubic as distance of OO intra-tissue 8% longer (at 0.1 MPa) to allow interpenetration. The cubic unit cell has a side length of 3.3501 Æ'... (for D 2 O, at 2.6 GPa and 22Ã, Â ° C (72Ã, Â ° F; 295Ã, K)) and contains two water molecules.
Ice VII is the only irregular ice phase that can be ordered with simple cooling, and forms (ordered) ice VIII below 273 K to ~ 8 GPa. Above this pressure, the transition temperature VII-VIII falls rapidly, reaching 0 K at ~ 60 GPa. Thus, ice VII has the largest stability field of all molecular phases of ice. The substrate of cubic oxygen that forms the backbone of the VII ice structure survives up to a pressure of at least 128 GPa; the pressure is substantially higher than where the water loses its entire molecular character, forming ice X. At high pressure, protonic diffusion (proton movements around the oxygen lattice) dominates the diffusion of molecules, a directly measured effect.
Video Ice VII
Natural events
The scientists hypothesized that ice VII could consist of the Titan sea floor as well as its extrasolar planets (such as Gliese 436 b, and Gliese 1214 b) made mostly of water.
By 2018, ice VII is identified among the inclusions found in natural diamonds. Because of this demonstration that ice VII exists in nature, the International Mineralogical Association actually classifies ice VII as a different mineral. Ice VII was probably formed when water trapped inside a diamond maintains a deep coat's high pressure due to the strength and stiffness of the diamond lattice, but is cooled to surface temperature, resulting in a high-pressure environment required without high temperatures.
Maps Ice VII
References
Karya dikutip
- Chaplin, Martin (2007-10-26). "Es-tujuh dan es-sepuluh struktur". Struktur Air dan Sains . Diperoleh 2008-01-02 .
Source of the article : Wikipedia
0 Comments