Ice II (Ice-two)

• can be formed from hexagonal Ice (Ice Ih) at 198 K and 3000 bar or by decompressing Ice-five (Ice V) at 238 K
• Ice II is likely to be a major rock-forming mineral in the outer Solar System
• It may form a major proportion of icy moons such as Jupiter’s Ganymede
• Density: 1.16 g/cm3

Structural features:

• Ice-two is a proton-ordered form of ice
• there are two types of 6-membered rings; one is almost flat (Type A) the other one has a more puckered, chair-like conformation (Type B)
• these two types of rings are strictly alternating stacked along the c axis

• If you look along the c axis, you will see that the two types of 6-rings are slightly rotated against each other (~ 16 degrees)

• Space group R-3
• Lattice parameters:
  • a = b = 12.935 Å, c = 6.233 Å
  • α = β = 90°, γ = 120°

  Here, you can download the CIF.

[Atomic structure figures created with VESTA:
K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).]

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