| Reference Type | Journal (article/letter/editorial) |
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| Title | Structural chemistry of NaCoPO₄ |
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| Journal | Acta Crystallographica Section B Structural Science |
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| Authors | Hammond, R. | Author |
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| Barbier, J. | Author |
| Year | 1996 (June 1) | Volume | 52 |
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| Page(s) | 440-449 | Issue | 3 |
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| Publisher | International Union of Crystallography (IUCr) |
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| URL | |
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| DOI | doi:10.1107/s0108768195016259Search in ResearchGate |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 189149 | Long-form Identifier | mindat:1:5:189149:6 |
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| GUID | 0 |
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| Full Reference | Hammond, R.; Barbier, J. (1996) Structural chemistry of NaCoPO₄. Acta Crystallographica Section B Structural Science, 52 (3). 440-449 doi:10.1107/s0108768195016259 |
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| Plain Text | Hammond, R.; Barbier, J. (1996) Structural chemistry of NaCoPO₄. Acta Crystallographica Section B Structural Science, 52 (3). 440-449 doi:10.1107/s0108768195016259 |
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| In | (1996, June) Acta Crystallographica Section B Structural Science Vol. 52 (3) International Union of Crystallography (IUCr) |
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| Abstract/Notes | Sodium cobalt phosphate, NaCoPO4, occurs as two different polymorphs which transform reversibly at 998 K. The crystal structures of both polymorphs have been determined by single-crystal X-ray diffraction. The low-temperature form α-NaCoPO4 crystallizes in the space group Pnma with cell parameters: a = 8.871 (3), b = 6.780 (3), c = 5.023 (1) Å, and Z = 4 [wR(F 2) = 0.0653 for all 945 independent reflections]. The α-phase contains octahedrally coordinated Co and Na atoms and tetrahedrally coordinated P atoms, and is isostructural with maracite, NaMnPO4. The structure of high-temperature β-NaCoPO4 is hexagonal with space group P65 and cell parameters: a = 10.166 (1), c = 23.881 (5) Å, and Z = 24 [wR(F 2) = 0.0867 for 4343 unique reflections]. The β-phase belongs to the large family of stuffed tridymites, with the P and Co atoms occupying tetrahedral sites and the Na atoms located in the cavities of the tetrahedral framework. The long c axis corresponds to a 3 × superstructure of the basic tridymite framework (c ≃ 8 Å) and is caused by the displacement of the Na atoms, tetrahedral tilts and strong distortions of the CoO4 tetrahedra. A bond-valence analysis of these phases reveals that the polymorphism in NaCoPO4 is due in part to over-/underbonding of the Na atom in the low-/high-temperature structures, respectively. |
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