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Crystal Lab4AB · ABC Chemistry

Crystal Lab › Oxides & frameworks

Corundum Al₂O₃

A₂B₃ · space group R-₃c (No. 167) · Z = 6

Unit cell

Lattice constants: a = 4.759 Å, b = 4.759 Å, c = 12.991 Å; α = 90°, β = 90°, γ = 120°
Cell volume: 254.8 Å³
Atoms in the cell: 30 (Al 12, O 18)
Formula units Z: 6
Calculated density: 3.99 g cm⁻³
Shortest contact: 1.856 Å

Coordination

Al: CN 6 at 1.86 Å (6 O)
O: CN 4 at 1.86 Å (4 Al)

About the structure

hcp array of O²⁻ with Al³⁺ in ⅔ of the octahedral holes.
Coordination: Al 6, O 4.
The hexagonal cell holds 6 formula units; Cr₂O₃, Fe₂O₃ (haematite), Ti₂O₃, V₂O₃ share the structure.
Ruby and sapphire are corundum with Cr³⁺ or Fe/Ti impurities.

Atom positions (fractional, one cell)

Atom	x	y	z
Al	0.0000	0.0000	0.3520
Al	0.6667	0.3333	0.6853
Al	0.3333	0.6667	0.0187
Al	0.0000	0.0000	0.1480
Al	0.6667	0.3333	0.4813
Al	0.3333	0.6667	0.8147
Al	0.0000	0.0000	0.6480
Al	0.6667	0.3333	0.9813
Al	0.3333	0.6667	0.3147
Al	0.0000	0.0000	0.8520
Al	0.6667	0.3333	0.1853
Al	0.3333	0.6667	0.5187
O	0.3060	0.0000	0.2500
O	0.9727	0.3333	0.5833
O	0.6393	0.6667	0.9167
O	0.0000	0.3060	0.2500
O	0.6667	0.6393	0.5833
O	0.3333	0.9727	0.9167
O	0.6940	0.6940	0.2500
O	0.3607	0.0273	0.5833
O	0.0273	0.3607	0.9167
O	0.6940	0.0000	0.7500
O	0.3607	0.3333	0.0833
O	0.0273	0.6667	0.4167
O	0.0000	0.6940	0.7500
O	0.6667	0.0273	0.0833
O	0.3333	0.3607	0.4167
O	0.3060	0.3060	0.7500
O	0.9727	0.6393	0.0833
O	0.6393	0.9727	0.4167

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

Other oxides & frameworks

Perovskite (ideal cubic)SrTiO₃ · ABO₃ Rhenium trioxideReO₃ · AB₃ SpinelMgAl₂O₄ · AB₂O₄ CupriteCu₂O · A₂B PyriteFeS₂ · AB₂ with S₂²⁻ pairs CalciteCaCO₃ · Carbonate MolybdeniteMoS₂ · Layered AB₂, 6:3 ScheeliteCaWO₄ · ABO₄ tetrahedral oxo-anion Magnetite (inverse spinel)Fe₃O₄ · Inverse spinel AB₂O₄ Ice Ih (oxygen framework)H₂O · Hydrogen-bonded network

Open Corundum in the 3D viewer → · All structures