Sodium hexahydridoaluminate Na₃AlH₆

Unit cell

Lattice constants

a = 5.210 Å, b = 5.420 Å, c = 7.500 Å; α = 90°, β = 89.86°, γ = 90°

Cell volume

211.8 ų

Atoms in the cell

20 (H 12, Al 2, Na 6)

Formula units Z

2

Calculated density

1.60 g cm⁻³

Shortest contact

1.745 Å

Coordination

H

CN 1 at 1.75 Å (1 Al)

Al

CN 6 at 1.74 Å (6 H)

Na

CN 5 at 2.20 Å (5.33 H)

About the structure

• Isolated [AlH₆]³⁻ octahedra with Na⁺ in the gaps — the cryolite (Na₃AlF₆) structure with hydride in place of fluoride.
• The intermediate in sodium alanate hydrogen storage: NaAlH₄ → ⅓ Na₃AlH₆ + ⅔ Al + H₂ → NaH + Al + 3/2 H₂; Ti doping makes both steps reversible.
• Coordinates from the Crystallography Open Database, entry 1533931 (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.