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The ReO3-type structure NbO2F, niobium dioxyfluoride, has been studied at high pressures using diamond anvil cells and synchrotron X-ray radiation. High-pressure powder diffraction measurements have been performed up to 40.1 GPa. A phase transition from the cubic (Pm3m) ambient pressure structure to a rhombohedral (R3c) structure at 0.47 GPa has been observed. Rietveld refinements at 1.38, 1.96, 3.20, 6.23, 9.00 and 10.5 GPa showed that the transition involves an a-a-a- tilting of the cation-anion coordination octahedra and a change of the anion-anion arrangement to approach hexagonal close packing. Compression and distortion of the Nb(O/F)6 octahedra is also revealed by the Rietveld refinements. At 17-18 GPa, the diffraction pattern disappears and the structure becomes X-ray amorphous.
Supporting information
Crystal data top
| FNbO2 | a = 5.52 Å |
| Mr = 143.9 | c = 13.52 Å |
| Trigonal, R3c | V = 356.46 Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.079 (11) | |
| O | 0.5 | 0 | 0.25 | 0.016 (3) | |
| F | 0.5 | 0 | 0.25 | 0.016 (3) | |
Geometric parameters (Å, º) top
| Nb—O | 1.951 | Nb—Nb | 3.902 |
| Nb—F | 1.951 | O—F | 2.759 |
| | | |
| O—Nb—F | 90 | Nb—O—Nb | 180 |
| O—Nb—F | 180 | | |
Crystal data top
| FNbO2 | a = 5.3067 (4) Å |
| Mr = 143.9 | c = 13.5495 (8) Å |
| Trigonal, R3c | V = 330.45 (3) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.079 (11) | |
| O | 0.4232 (17) | 0 | 0.25 | 0.016 (3) | |
| F | 0.4232 (17) | 0 | 0.25 | 0.016 (3) | |
Geometric parameters (Å, º) top
| Nb—O | 1.946 (1) | O—F | 2.746 (5) |
| Nb—F | 1.946 (1) | O—F | 2.759 (4) |
| Nb—Nb | 3.8061 (4) | O—F | 3.290 (4) |
| O—F | 2.745 (6) | | |
| | | |
| O—Nb—F | 89.7 | O—Nb—F | 180.0 (5) |
| O—Nb—F | 90.3 | Nb—O—Nb | 155.8 (3) |
Crystal data top
| FNbO2 | a = 5.2357 (3) Å |
| Mr = 143.9 | c = 13.5542 (12) Å |
| Trigonal, R3c | V = 321.78 (2) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.0266 (8) | |
| O | 0.4112 (9) | 0 | 0.25 | 0.0031 (18) | |
| F | 0.4112 (9) | 0 | 0.25 | 0.0031 (18) | |
Geometric parameters (Å, º) top
| Nb—O | 1.943 (1) | O—F | 2.757 (3) |
| Nb—F | 1.944 (4) | O—F | 2.758 (4) |
| Nb—Nb | 3.7737 (3) | O—F | 3.119 (4) |
| O—F | 2.739 (6) | | |
| | | |
| O—Nb—F | 89.6 (2) | O—Nb—F | 180.0 (5) |
| O—Nb—F | 90.4 (2) | Nb—O—Nb | 152.3 (3) |
Crystal data top
| FNbO2 | a = 5.1232 (4) Å |
| Mr = 143.9 | c = 13.6017 (17) Å |
| Trigonal, R3c | V = 309.18 (2) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.0208 (5) | |
| O | 0.3912 (8) | 0 | 0.25 | 0.0074 (18) | |
| F | 0.3912 (8) | 0 | 0.25 | 0.0074 (18) | |
Geometric parameters (Å, º) top
| Nb—O | 1.945 (2) | O—F | 2.738 (4) |
| Nb—F | 1.945 (5) | O—F | 2.763 (3) |
| Nb—Nb | 3.7267 | O—F | 2.764 (4) |
| O—F | 2.737 (5) | | |
| | | |
| O—Nb—F | 89.5 (1) | O—Nb—F | 180.0 (7) |
| O—Nb—F | 90.5 (1) | Nb—O—Nb | 146.7 (2) |
Crystal data top
| FNbO2 | a = 4.9462 (4) Å |
| Mr = 143.9 | c = 13.6689 (18) Å |
| Trigonal, R3c | V = 289.60 (2) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.0359 (6) | |
| O | 0.3748 (6) | 0 | 0.25 | 0.0143 (12) | |
| F | 0.3748 (6) | 0 | 0.25 | 0.0143 (12) | |
Geometric parameters (Å, º) top
| Nb—O | 1.929 (1) | O—F | 2.759 (2) |
| Nb—F | 1.929 (2) | O—F | 2.958 (2) |
| Nb—Nb | 3.6531 (3) | O—F | 3.211 (2) |
| O—F | 2.696 (6) | | |
| | | |
| O—Nb—F | 88.7 (1) | O—Nb—F | 180 (1) |
| O—Nb—F | 91.3 (1) | Nb—O—Nb | 142.5 (2) |
Crystal data top
| FNbO2 | a = 4.8552 (3) Å |
| Mr = 143.9 | c = 13.7000 (14) Å |
| Trigonal, R3c | V = 279.68 (2) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.0315 (7) | |
| O | 0.3674 (6) | 0 | 0.25 | 0.0127 (13) | |
| F | 0.3674 (6) | 0 | 0.25 | 0.0127 (13) | |
Geometric parameters (Å, º) top
| Nb—O | 1.919 (1) | O—F | 2.672 (3) |
| Nb—F | 1.991 (2) | O—F | 2.755 (2) |
| Nb—Nb | 3.6154 (4) | O—F | 2.756 (2) |
| O—F | 2.671 (4) | O—F | 2.912 (2) |
| | | |
| O—Nb—F | 88.2 (1) | O—Nb—F | 180.0 (2) |
| O—Nb—F | 91.8 (1) | Nb—O—Nb | 140.8 (2) |
Crystal data top
| FNbO2 | a = 4.8232 (3) Å |
| Mr = 143.9 | c = 13.7125 (18) Å |
| Trigonal, R3c | V = 276.26 (2) Å3 |
| Hall symbol: -R 3 2"c | Z = 6 |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| Nb | 0 | 0 | 0 | 0.0302 (8) | |
| O | 0.3675 (7) | 0 | 0.25 | 0.0130 (15) | |
| F | 0.3675 (7) | 0 | 0.25 | 0.0130 (15) | |
Geometric parameters (Å, º) top
| Nb—O | 1.911 (1) | O—F | 2.654 (4) |
| Nb—F | 1.911 (3) | O—F | 2.751 (2) |
| Nb—Nb | 3.6024 (5) | O—F | 2.752 (3) |
| O—F | 2.653 (4) | O—F | 2.906 (2) |
| | | |
| O—Nb—F | 87.9 (1) | O—Nb—F | 180.0 (1) |
| O—Nb—F | 92.1 (1) | Nb—O—Nb | 140.9 (2) |
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