Ice VI

Phase diagram of water
  • Can be formed from liquid water at 11 kbar by lowering the temperature to approx. -3 °C
  • Density: 1.31 g/cm3

Structural features

Crystal structure of Ice VI
  • Ice VI is a proton-disordered phase
  • it is composed of two independent interpenetrating networks of H-bonded water molecules (shown above in blue and red, respectively)
  • the main structural motif is a tricyclic, cage-like water hexamer, similar as in liquid water
A tricyclic water hexamer composed of four-membered rings
  • This motif is also found for the silicon atoms in the zeolite edingtonite, see here for comparison.
  • The respective topology of the underlying net is edi, a binodal (4,4)-c net with transitivity pqrs = 2343
  • Space group: P42/nmc (No. 137)
  • Crystal system: Tetragonal
  • Lattice parameters:
    • a = b = 6.116(1) Å, c = 5.689(1) Å
    • α = β = γ = 90°

Literature:

[1] W. F. Kuhs, J. L. Finney, C. Vettier and D. V. Bliss, Structure and hydrogen ordering in ices VI, VII and VIII by neutron powder diffraction. J. Chem. Phys. 1984, 81, 3612-3623.
DOI: 10.1063/1.448109

Here, you can download the CIF.

Atomistic structure figures were 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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