Ice Xvi

Short description: Alternative state of water ice

Ice XVI. White edges mark the unit cell (~17 Å).

Ice XVI is the least dense (0.81 g/cm³)^[1] experimentally obtained crystalline form of ice. It is topologically equivalent to the empty structure of sII clathrate hydrates. It was first obtained in 2014 by removing gas molecules from a neon clathrate under vacuum at temperatures below 147 K.^[1] The resulting empty water frame, ice XVI, is thermodynamically unstable at the experimental conditions, yet it can be preserved at cryogenic temperatures. Above 145–147 K at positive pressures ice XVI transforms into the stacking-faulty ice I_c and further into ordinary ice I_h. Theoretical studies predict ice XVI to be thermodynamically stable at negative pressures (that is under tension).^[2]^[3]

Water phase diagram extended to negative pressures calculated with TIP4P/2005 model.^[2]

References

↑ ^1.0 ^1.1 Falenty, A.; Hansen, T. C.; Kuhs, W. F. (2014). "Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate". Nature 516 (7530): 231–233. doi:10.1038/nature14014. PMID 25503235. Bibcode: 2014Natur.516..231F.
↑ ^2.0 ^2.1 Conde, M.M.; Vega, C.; Tribello, G.A.; Slater, B. (2009). "The phase diagram of water at negative pressures: Virtual ices". The Journal of Chemical Physics 131 (34510): 034510. doi:10.1063/1.3182727. PMID 19624212. Bibcode: 2009JChPh.131c4510C.
↑ Jacobson, Liam C.; Hujo, Waldemar; Molinero, Valeria (2009). "Thermodynamic Stability and Growth of Guest-Free Clathrate Hydrates: A Low-Density Crystal Phase of Water". Journal of Physical Chemistry B 113 (30): 10298–10307. doi:10.1021/jp903439a. PMID 19585976.

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[falenty2014-1] 1.0 ^1.1 Falenty, A.; Hansen, T. C.; Kuhs, W. F. (2014). "Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate". Nature 516 (7530): 231–233. doi:10.1038/nature14014. PMID 25503235. Bibcode: 2014Natur.516..231F.

[conde2009-2] 2.0 ^2.1 Conde, M.M.; Vega, C.; Tribello, G.A.; Slater, B. (2009). "The phase diagram of water at negative pressures: Virtual ices". The Journal of Chemical Physics 131 (34510): 034510. doi:10.1063/1.3182727. PMID 19624212. Bibcode: 2009JChPh.131c4510C.

[jacobson2009-3] Jacobson, Liam C.; Hujo, Waldemar; Molinero, Valeria (2009). "Thermodynamic Stability and Growth of Guest-Free Clathrate Hydrates: A Low-Density Crystal Phase of Water". Journal of Physical Chemistry B 113 (30): 10298–10307. doi:10.1021/jp903439a. PMID 19585976.