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Ice-fourteen crystal structure

Ice-fourteen crystal structure[1002]
Ice XIV (Ice-fourteen)

 

Ice-fourteen (ice XIV) is the proton-ordered form of ice-twelve, formed by doping with 10 mM HCl (about one molecule to every 5000 molecules of water; as DCl with D2O) below 118 K and at 1.2 GPa to facilitate the phase transition [1002]. The transformation is reversible with temperature change, but less proton-ordering of ice-fourteen is found at lower pressure [1081]. The crystals were orthorhombic P212121 with cell dimensions a 8.350 Å, b 8.139 Å and c 4.083 Å (90°, 90°, 90°, 12 molecules; at atmospheric pressure and 80 K) and a unit cell contains 12 water molecules [1002]. 8 out of the 24 proton positions in the unit cell (as some labeled * opposite forming chains; the shown ordering of these is predominant) remained mostly disordered. Dielectric spectroscopy studies have shown that the transition from disordered ice-twelve to fully ordered ice-fourteen is composed of a fast component, yielding ~30% of the expected entropy loss followed by a slow component achieving full order, in the presence of HCl catalysis [2353].

 

It is possible that two further metastable proton ordered forms of ice XIV may form under kinetically controlled conditions, as shown by simulations [1105].

 

Interactive Jmol structures are given.

 

 

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This page was established in 2006 and last updated by Martin Chaplin on 5 November, 2017


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