Table 3. Results of the Rietveld Refinement of Na3NiH5 Polymorphs under Different p, T Conditions.
| phase | LP Na3NiH5 | HT-HP Na3NiH5 | LT-HP Na3NiH5 | LT-HP Na3NiH5 |
| temperature | RT (300 K) | 365 °C (638 K) | 320 °C (593 K) | RT (300 K) |
| pressure | ambient | ∼5 GPa | ∼5 GPa | ∼4.4 GPa |
| crystal system | orthorhombic | cubic | orthorhombic | orthorhombic |
| space group | Pnma (62) | Fm3̅m (225) | Cmcm (63) | Cmcm (63) |
| Z | 4 | 4 | 4 | 4 |
| lattice parameters (Å) | a = 10.4131(9) | a = 7.16905(16) | a = 7.3444(9) | a = 7.3575(13) |
| b = 7.3711(6) | b = 6.8828(9) | b = 6.7932(15) | ||
| c = 5.4291(5) | c = 7.2247(8) | c = 7.2231(12) | ||
| V (Å3) | 416.71(6) | 368.456(15) | 365.21(8) | 361.02(12) |
| V/Z (Å3) | 104.18 | 92.114 | 91.303 | 90.255 |
| formula weight | 132.7 | 132.7 | 132.7 | 132.7 |
| dcalc (g/cm3) | 2.115 | 2.392 | 2.413 | 2.442 |
| Robs (%) | 5.94 | 6.41 | 8.35 | 10.94 |
| Rall (%) | 5.94 | 6.41 | 8.71 | 11.10 |