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.