Ice XV is the hydrogen-bonding ordered form of the ice VI phase. Its existence was surmised based on the presence of the ordered forms of other ices at low temperatures. Its structure, using the fully deuterated form (D2O) was first described in 2009 . It was prepared by using 0.01 M DCl (deuterated hydrochloric acid) as a dopant to help the ordering rearrangement of the hydrogen bonding at low temperatures (<130 K).
Ice XV is antiferroelectric with all the water molecule dipoles cancelling out as each of the two separate
interpenetrating networks possess oppositely aligned hydrogen bonding.
crystal (shown opposite), is in space group, has cell dimensions a = 6.2323 Å, b = 6.2438
Å, c = 5.7903 Å (90.06º, 89.99º, 89.92º;
D2O, at ~0.9 GPa and 80 K) .
Ice-fifteen has triple points with ice-six
and ice-two (estimated at 130 K, 0.8 GPa), and ice-six
and ice-eight (estimated at 130 K, 1.5 GPa) .
Interactive Jmol structures of ice VI and ice XV are given.