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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Ice V and XIII

• can be formed by slowly cooling liquid water at ~ 5 kbar from 20 °C to – 20 °C
• density: 1.23 g/cm³

Structural features

• Ice V is a proton-disordered phase
• the analogous proton-ordered phase is Ice XIII
• all water molecules are hydrogen-bonded to four others, two as donor and two as acceptor, at distances of 2.76 to 2.87 Å
• the coordination tetrahedra are largely distorted with angles ranging from 84 to 128°.
• Ice V contains 4,- 5-, 6-, and 7-membered rings
• Space group: A2/a (No. 15)
• Crystal system: monoclinic
• Lattice parameters:
  • a = 9.22(2) Å, b = 7.54(1) Å, c = 10.35(2) Å
  • α = γ = 90°, β =109.2(2)°
  • 28 molecules per unit cell

 Here, you can download the CIF.

Literature:

[1] B. Kamb, A. Prakash, C. Knobler, Structure of Ice V, Acta Cryst. 1967, 22, 706-715. DOI: 10.1107/S0365110X67001409

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).

Ice IV – a remarkable self-interpenetrating structure

Ice IV (Ice four)

• metastable in the phase space between Ice III, Ice V and Ice VI (see orange circle in the Figure above)
• may be formed from high-density amorphous ice by slow heating from 145 K and a constant pressure of 8 kbar
• calc. density at 110 K and 1 bar = 1.27 g/cm³

Structural features

• proton-disordered phase
• all water molecules are hydrogen-bonded to four others, two as donor and two as acceptor
• exclusively 6-membered rings (two types, one almost flat, the other more puckered)
• the most striking structural feature is that Ice IV builds a self-interpenetrating structure, but this does not consists of two independent networks but of only one net: two water molecules (shown in blue in the following Figure) bonded by H-bonds are oriented perpendicular and are running through the center of the almost flat 6-membered rings:

• Space group: R-3c (No. 167)
• Crystal system: trigonal
• Lattice parameters:
  • a = b = 8.72922 Å, c = 17.06581 Å
  • α = β = 90°, γ =120°

 Here, you can download the CIF.

Literature:

[1] H. Engelhardt and B. Kamb, Structure of ice IV, a metastable high-pressure phase, Journal of Chemical Physics 1981, 75, 5887-5899. DOI: 10.1063/1.442040

[2] C. G. Salzmann, I. Kohl, T. Loerting, E. Mayer and A. Hallbrucker, Raman spectroscopic study on hydrogen-bonding in recovered ice IV, Journal of Physical Chemistry B 2003, 107, 2802-2807. DOI: 10.1021/jp021534k

 

[Atomistic 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).

and

CrystalMaker®.]

Ice III and IX

Ice III and IX (Ice three and Ice nine)

• Ice III can be formed from liquid water at 300 MPa (3000 bar) by lowering the temperature to approx. 250 K.
• The relative permittivity is very high (~ 117)
• Density: 1.16 g/cm³

Structural features

• Ice III is also called Keatite Ice, because the oxygen atoms are located at analogous positions of the silicon atoms in the SiO₂ phase Keatite.
• Ice IX is the proton-ordered form of Ice III.
• The tetrahedral environment of the water molecules are considerably distorted.
• Interestingly, there are no 6-membered rings present anymore, but 5, 7, and 8 –membered rings instead. The 5-membered rings can be best seen if you look along the a or b direction:

 

• • Two-third of the water molecules are forming 4₁ helices/screws running along the c axis, which means that Ice III is chiral! The other water molecules connect these helices and are forming a 2₁ helix.

 

• Space group: P4₁2₁2 (No. 92)
• Crystal system: tetragonal
• Lattice parameters:
  • a = b = 6.73(1) Å, c = 6.83(1) Å
  • α = β = γ = 90°

 

 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).

and

CrystalMaker®.

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).]

Ice Ic

Ice Ic ( Ice one cubic)

• can be formed by condensation of water vapour at reduced pressure well below -80 °C
• is metastable with respect to Ice Ih (approx. + 50 J/mol)
• it seems to be very difficult to grow large phase-pure Ic ice crystals; they contain, to a certain extent stacking-disordered or hexagonal ice

Structural features:

• like hexagonal ice cubic ice is a proton-disordered phase
• every water molecule is involved in 4 H-bonds (2 acceptors, 2 donors)
• tetrahedrally coordinated
• O-D bond length approx. 101 pm
• D …. O-D distance approx. 174 pm
• O … O distance approx. 275 pm
• 6-membered rings (exclusively chair conformation)

• sometimes also called “cristobalite ice” because the oxygen atoms occupy the Si analogeous positions in the SiO₂ phase cristobalite
• it would be also justified to call it diamond-like ice 🙂
• Space group Fd-3m
  • a = b = c = 6.3510 Å
  • α = β = γ = 90°

 

  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).]

Ice Ih

Ice I_h (Ice one hexagonal)

Structural features:

• single molecule and molecular arrangement

• Ice Ih is a proton-disordered phase

• every water molecule is involved in 4 H-bonds (2 acceptors, 2 donors)
• tetrahedrally coordinated
• O-H bond length approx. 99 pm
• H …. O-H distance approx. 175 pm
• O … O distance approx. 275 pm
• H-bond strength: approx. 21 kJ/mol
• 6-membered rings
  • chair-like conformation in the (a,b) plane
  • boat-like conformation along the c direction

(graphic 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).

• sometimes called “tridymite ice” because the oxygen atoms occupy the Si analogeous positions in the SiO₂ phase tridymite
• Space group P6₃/mmc
  • a = b = 4.4975 Å, c = 7.3224 Å
  • α = β = 90°, γ = 120°

 Here, you can download the CIF.