Crystal Lab › Hydrides & storage
Sodium alanate NaAlH₄
Complex hydride (scheelite-type) · space group I41/a:2 (No. 88) · Z = 4
Unit cell
- Lattice constants
- a = 4.830 Å, b = 4.830 Å, c = 10.560 Å; α = 90°, β = 90°, γ = 90°
- Cell volume
- 246.4 ų
- Atoms in the cell
- 24 (Na 4, Al 4, H 16)
- Formula units Z
- 4
- Calculated density
- 1.46 g cm⁻³
- Shortest contact
- 1.634 Å
Coordination
- Na
- CN 8 at 2.28 Å (8 H)
- Al
- CN 4 at 1.63 Å (4 H)
- H
- CN 1 at 1.63 Å (1 Al)
About the structure
- Isolated AlH₄⁻ tetrahedra with Na⁺ between them — the scheelite (CaWO₄) arrangement with AlH₄⁻ in place of WO₄²⁻.
- Releases hydrogen in steps (NaAlH₄ → Na₃AlH₆ → NaH), 5.6 wt % in total; Ti doping makes the steps reversible — the discovery that started modern complex-hydride storage.
- Coordinates from the Crystallography Open Database, entry 1533929 (open data); hydrogen and water sites with partial occupancy below 0.5 are left out.
Atom positions (fractional, one cell)
| Atom | x | y | z |
|---|---|---|---|
| Na | 0.0000 | 0.2500 | 0.1250 |
| Na | 0.5000 | 0.2500 | 0.3750 |
| Na | 0.5000 | 0.7500 | 0.6250 |
| Na | 0.0000 | 0.7500 | 0.8750 |
| Al | 0.0000 | 0.2500 | 0.6250 |
| Al | 0.5000 | 0.2500 | 0.8750 |
| Al | 0.5000 | 0.7500 | 0.1250 |
| Al | 0.0000 | 0.7500 | 0.3750 |
| H | 0.2626 | 0.5967 | 0.0400 |
| H | 0.1533 | 0.5126 | 0.2900 |
| H | 0.2374 | 0.4033 | 0.5400 |
| H | 0.3467 | 0.4874 | 0.7900 |
| H | 0.7374 | 0.4033 | 0.9600 |
| H | 0.8467 | 0.4874 | 0.7100 |
| H | 0.7626 | 0.5967 | 0.4600 |
| H | 0.6533 | 0.5126 | 0.2100 |
| H | 0.7626 | 0.0967 | 0.5400 |
| H | 0.6533 | 0.0126 | 0.7900 |
| H | 0.7374 | 0.9033 | 0.0400 |
| H | 0.8467 | 0.9874 | 0.2900 |
| H | 0.2374 | 0.9033 | 0.4600 |
| H | 0.3467 | 0.9874 | 0.2100 |
| H | 0.2626 | 0.0967 | 0.9600 |
| H | 0.1533 | 0.0126 | 0.7100 |
Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.