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词条 Ice VII
释义

  1. Natural occurrence

  2. References

  3. External links

Ice VII is a cubic crystalline form of ice. It can be formed from liquid water above 3 GPa (30,000 atmospheres) by lowering its temperature to room temperature, or by decompressing heavy water (D2O) ice VI below 95 K. Ordinary water ice is known as ice Ih, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XVI, have been created in the laboratory at different temperatures and pressures. Ice VII is metastable over a wide range of temperatures and pressures and transforms into low-density amorphous ice (LDA) above {{Convert|120|K|C}}.[1] Ice VII has a triple point with liquid water and ice VI at 355 K and 2.216 GPa, with the melt line extending to at least {{Convert|715|K|C}} and 10 GPa.[2] Ice VII can be formed within nanoseconds by rapid compression via shock-waves.[3][4] It can also be created by increasing the pressure on ice VI at ambient temperature.[5]

Like the majority of ice phases (including ice Ih), the hydrogen atom positions are disordered.[6] In addition, the oxygen atoms are disordered over multiple sites.[7][8][9] The structure of ice VII comprises a hydrogen bond framework in the form of two interpenetrating (but non-bonded) sublattices.[7] Hydrogen bonds pass through the center of the water hexamers and thus do not connect the two lattices. Ice VII has a density of about 1.65 g cm−3 (at 2.5 GPa and {{Convert|25|C|F K}}),[10] which is less than twice the cubic ice density as the intra-network O–O distances are 8% longer (at 0.1 MPa) to allow for interpenetration. The cubic unit cell has a side length of 3.3501 Å (for D2O, at 2.6 GPa and {{Convert|22|C|F K}}) and contains two water molecules.[8]

Ice VII is the only disordered phase of ice that can be ordered by simple cooling,[5][11] and it forms (ordered) ice VIII below 273 K up to ~8 GPa. Above this pressure, the VII–VIII transition temperature drops rapidly, reaching 0 K at ~60 GPa.[12] Thus, ice VII has the largest stability field of all of the molecular phases of ice. The cubic oxygen sub-lattices that form the backbone of the ice VII structure persist to pressures of at least 128 GPa;[13] this pressure is substantially higher than that at which water loses its molecular character entirely, forming ice X. In high pressure ices, protonic diffusion (movement of protons around the oxygen lattice) dominates molecular diffusion, an effect which has been measured directly.[14]Minh

Natural occurrence

Scientists hypothesize that ice VII may comprise the ocean floor of Europa as well as extrasolar planets (such as Gliese 436 b, and Gliese 1214 b) that are largely made of water.[15][16]

In 2018, ice VII was identified among inclusions found in natural diamonds. Due to this demonstration that ice VII exists in nature, the International Mineralogical Association duly classified ice VII as a distinct mineral.[17] The ice VII was presumably formed when water trapped inside the diamonds retained the high pressure of the deep mantle due to the strength and rigidity of the diamond lattice, but cooled down to surface temperatures, producing the required environment of high pressure without high temperature.[18]

References

1. ^S. Klotz, J. M. Besson, G. Hamel, R. J. Nelmes, J. S. Loveday and W. G. Marshall, Metastable ice VII at low temperature and ambient pressure, Nature 398 (1999) 681–684.
2. ^{{cite web | url = http://www.iapws.org/relguide/meltsub.pdf | title = IAPWS, Release on the pressure along the melting and the sublimation curves of ordinary water substance, 1993 | accessdate = 2008-02-22 | deadurl = yes | archiveurl = https://web.archive.org/web/20081006141126/http://www.iapws.org/relguide/meltsub.pdf | archivedate = 2008-10-06 | df = }}
3. ^{{cite journal | last1 = Dolan | first1 = D | last2 = Gupta | first2 = Y | title = Nanosecond freezing of water under multiple shock wave compression: Optical transmission and imaging measurements | journal = J. Chem. Phys. | volume = 121 | issue = 18 | pages = 9050–9057 | year = 2004 | doi = 10.1063/1.1805499 | pmid = 15527371 | bibcode = 2004JChPh.121.9050D }}
4. ^{{cite journal | last1 = Myint | first1 = P | last2 = Benedict | first2 = L | last3 = Belof | first3 = J | title = Free energy models for ice VII and liquid water derived from pressure, entropy, and heat capacity relations | journal = J. Chem. Phys. | volume = 147 | issue = 8 | pages = 084505 | year = 2017 | doi = 10.1063/1.4989582 | pmid = 28863506 | bibcode = 2017JChPh.147h4505M }}
5. ^1 {{Citation |first=G. P. |last=Johari |first2=A. |last2=Lavergne |first3=E. |last3=Whalley |lastauthoramp=yes |journal=Journal of Chemical Physics |volume=61 |issue=10 |pages=4292 |year=1974 |title=Dielectric properties of ice VII and VIII and the phase boundary between ice VI and VII |doi=10.1063/1.1681733 |bibcode = 1974JChPh..61.4292J }}
6. ^{{Citation |first=V. F. |last=Petrenko |first2=R. W. |last2=Whitworth |title=The Physics of Ice |publisher=Oxford University Press |location=New York |year=2002 }}.
7. ^1 {{Citation |first=W. F. |last=Kuhs |first2=J. L. |last2=Finney |first3=C. |last3=Vettier |first4=D. V. |last4=Bliss |lastauthoramp=yes |journal=Journal of Chemical Physics |volume=81 |issue=8 |pages=3612–3623 |year=1984 |title=Structure and hydrogen ordering in ices VI, VII, and VIII by neutron powder diffraction |doi=10.1063/1.448109 |bibcode = 1984JChPh..81.3612K }}.
8. ^1 {{Citation |first=J. D. |last=Jorgensen |first2=T. G. |last2=Worlton |journal=Journal of Chemical Physics |volume=83 |issue=1 |pages=329–333 |year=1985 |title=Disordered structure of D2O ice VII from in situ neutron powder diffraction |doi=10.1063/1.449867 |bibcode = 1985JChPh..83..329J |url=https://zenodo.org/record/1232091/files/article.pdf }}.
9. ^{{Citation |first=R. J. |last=Nelmes |first2=J. S. |last2=Loveday |first3=W. G. |last3=Marshall |journal=Physical Review Letters |volume=81 |issue=13 |pages=2719–2722 |year=1998 |title=Multisite Disordered Structure of Ice VII to 20 GPa |doi=10.1103/PhysRevLett.81.2719 |bibcode=1998PhRvL..81.2719N|display-authors=etal}}.
10. ^D. Eisenberg and W. Kauzmann, The structure and properties of water (Oxford University Press, London, 1969); (b) The dodecahedral interstitial model is described in L. Pauling, The structure of water, In Hydrogen bonding, Ed. D. Hadzi and H. W. Thompson (Pergamon Press Ltd, London, 1959) pp 1–6.
11. ^Note: ice Ih theoretically transforms into proton-ordered ice XI on geologic timescales, but in practice it is necessary to add small amounts of KOH catalyst.
12. ^{{Citation |first=Ph. |last=Pruzan |first2=J. C. |last2=Chervin |first3=B. |last3=Canny |lastauthoramp=yes |journal=Journal of Chemical Physics |volume=99 |issue=12 |pages=9842–9846 |year=1993 |title=Stability domain of the ice VIII proton-ordered phase at very high pressure and low temperature |doi=10.1063/1.465467 |bibcode = 1993JChPh..99.9842P }}.
13. ^{{Citation |first=R. J. |last=Hemley |first2=A. P. |last2=Jephcoat |first3=H. K. |last3=Mao |journal=Nature |issue=6150 |volume=330 |pages=737–740 |year=1987 |title=Static compression of H2O-ice to 128 GPa (1.28 Mbar) |doi=10.1038/330737a0 |bibcode = 1987Natur.330..737H |display-authors=etal}}.
14. ^{{cite journal|last=Katoh|first=E.|title=Protonic Diffusion in High-Pressure Ice VII|journal=Science|date=15 February 2002 |volume=29=5558|issue=5558|pages=1264–1266|doi=10.1126/science.1067746|bibcode = 2002Sci...295.1264K|pmid=11847334}}
15. ^University of Liège (2007, May 16). Astronomers Detect Shadow Of Water World In Front Of Nearby Star. ScienceDaily. Retrieved Jan. 3, 2010, from {{cite web |url=https://www.sciencedaily.com/releases/2007/05/070516151053.htm |title=Archived copy |accessdate=2018-04-22 |deadurl=no |archiveurl=https://web.archive.org/web/20170821212607/https://www.sciencedaily.com/releases/2007/05/070516151053.htm |archivedate=2017-08-21 |df= }}
16. ^{{cite web |url=http://www.cfa.harvard.edu/news/2009/pr200924.html |title=Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology |author=David A. Aguilar |date=2009-12-16 |website= |publisher=Harvard-Smithsonian Center for Astrophysics |accessdate=January 23, 2010 |deadurl=no |archiveurl=https://www.webcitation.org/66sgAVTw2?url=http://www.cfa.harvard.edu/news/2009/pr200924.html |archivedate=April 13, 2012 |df= }}
17. ^{{cite journal|url=http://www.sciencemag.org/news/2018/03/pockets-water-may-lay-deep-below-earth-s-surface|title=Pockets of water may lay deep below Earth's surface|author=Sid Perkins|journal=Science|date=2018-03-08|accessdate=March 8, 2018|deadurl=no|archiveurl=https://web.archive.org/web/20180308220310/http://www.sciencemag.org/news/2018/03/pockets-water-may-lay-deep-below-earth-s-surface|archivedate=March 8, 2018|df=}}
18. ^{{cite news|last1=Netburn|first1=Deborah|title=What scientists found trapped in a diamond: a type of ice not known on Earth|url=http://www.latimes.com/science/sciencenow/la-sci-sn-water-in-diamonds-20180308-story.html|accessdate=12 March 2018|work=latimes.com|deadurl=no|archiveurl=https://web.archive.org/web/20180312003000/http://www.latimes.com/science/sciencenow/la-sci-sn-water-in-diamonds-20180308-story.html|archivedate=12 March 2018|df=}}

External links

  • {{cite web |first=Maren |last=Hunsberger |title=A New State of Water Reveals a Hidden Ocean in Earth's Mantle |date=September 21, 2018 |work=Seeker |url=https://www.youtube.com/watch?v=pgm4z8vJVVk |via=YouTube }}
  • {{cite web |first=Marcus |last=Woo |date=July 11, 2018 |title=The Hunt for Earth's Deep Hidden Oceans |work=Quanta Magazine |url=https://www.quantamagazine.org/the-hunt-for-earths-deep-hidden-oceans-20180711 }}
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1 : Water ice
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