page_title: Ice XVI
hierarchical_section_title: Ice XVI
caption_attribution_description: English: Water phase diagram extended to negative pressures. Phase boundaries at the negative pressure have been calculated with TIP4P/2005 model (after Conde et al., 2009). sH stands for a hypothetical expanded water structure topologically similar to sH clathrate hydrate
context_page_description: Ice XVI is the least dense 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. 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 Ic and further into ordinary ice Iₕ. Theoretical studies predict ice XVI to be thermodynamically stable at negative pressures.
context_section_description: Ice XVI is the least dense (0.81 g/cm³) 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. 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 Ic and further into ordinary ice Iₕ. Theoretical studies predict ice XVI to be thermodynamically stable at negative pressures (that is under tension).
caption: Water phase diagram extended to negative pressures calculated with TIP4P/2005 model.[2]
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