Low cristobalite SiO₂

Unit cell

Lattice constants

a = 4.964 Å, b = 4.964 Å, c = 6.920 Å; α = 90°, β = 90°, γ = 90°

Cell volume

170.5 ų

Atoms in the cell

12 (Si 4, O 8)

Formula units Z

4

Calculated density

1.25 g cm⁻³

Shortest contact

1.590 Å

Coordination

Si

CN 4 at 1.59 Å (4 O)

O

CN 2 at 1.59 Å (2 Si)

About the structure

• The SiO₂ polymorph with the diamond topology: Si atoms where carbon sits in diamond, O bridging every pair — high cristobalite is cubic, this low form is the slightly collapsed tetragonal version.
• Stable only above 1470 °C but survives as a metastable phase; also the structure of Si in silicon-based "cristobalite-like" oxides.
• Coordinates from the Crystallography Open Database, entry 1010938 (open data); hydrogen and water sites with partial occupancy below 0.5 are left out.

Atom positions (fractional, one cell)

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