Bismuth triiodide BiI₃

Unit cell

Lattice constants

a = 7.516 Å, b = 7.516 Å, c = 20.718 Å; α = 90°, β = 90°, γ = 120°

Cell volume

1013.6 ų

Atoms in the cell

24 (Bi 6, I 18)

Formula units Z

6

Calculated density

5.80 g cm⁻³

Shortest contact

3.045 Å

Coordination

Bi

CN 6 at 3.05 Å (6 I)

I

CN 2 at 3.05 Å (2 Bi)

About the structure

• Hexagonal close-packed I⁻ layers with Bi³⁺ filling two-thirds of the octahedral holes between every second pair of layers — an AB₃ layer structure, the iodide analogue of CdI₂ with one cation site in three left empty.
• The empty layers hold the sheets together only by van der Waals forces, so the crystal cleaves like mica; BiI₃ is a room-temperature X-ray and γ-ray detector material.
• Coordinates from the Crystallography Open Database, entry 8104287 (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.