Ice Ih (oxygen framework) H₂O

Unit cell

Lattice constants

a = 4.520 Å, b = 4.520 Å, c = 7.360 Å; α = 90°, β = 90°, γ = 120°

Cell volume

130.2 ų

Atoms in the cell

4 (O 4)

Formula units Z

4

Calculated density

0.92 g cm⁻³

Shortest contact

2.760 Å

Coordination

O

CN 4 at 2.76 Å (4 O)

About the structure

• Only the oxygen framework is shown: the hydrogens are disordered (each O–O line carries one H, placed at random under the Bernal–Fowler rules).
• Each O is tetrahedrally hydrogen-bonded to four others (O···O 2.76 Å) — the wurtzite/lonsdaleite framework.
• The open hexagonal channels are why ice is less dense than water.

Atom positions (fractional, one cell)

Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.