Calcium-lead fluoro-vanadinite apatites. II. Equilibrium structures

Zhi Li Dong; T. J. White

doi:10.1107/S0108768104001843

Calcium-lead fluoro-vanadinite apatites. II. Equilibrium structures

Zhi Li Dong^*, T. J. White

^*Corresponding author for this work

Nanyang Technological University

Research output: Contribution to journal › Article › peer-review

32 Citations (Scopus)

Abstract

The synthetic vanadinites (Pb_xCa_10-x)(VO ₄)₆(F_1-2yO_y□_y) ₂, 0.57 < x < 9 and 0.10 < y < 0.47, adopt the P6 ₃/m apatite structure with 9.7835 (3) ≤ a ≤ 10.0531 (1) Å and 7.0318 (2) ≤ c ≤ 7.3033 (1) Å. The calcium endmember is monoclinic, space group P2₁lm, with a = 9.7370 (3), b = 9.7358 (4), c = 7.00572 (9) Å, y= 120.002 (5)°. For mixed metal compounds (x ≠ 0) the partitioning of calcium and lead over the A^I(4f) and A ^II(6h) positions is nonstoichiometric, with lead preferentially favouring the larger A^II site at a partitioning coefficient k _Pb(A^I/A^II) ≃ 0.33 for all x < 7. A miscibility gap exists for 2 < x < 3. Trends in crystallographic parameters can be correlated through consideration of the A^IO ₆ metaprism twist angle (φ) that can be used to derive ideal cell parameters from triangular anion networks.

Original language	English
Pages (from-to)	146-154
Number of pages	9
Journal	Acta Crystallographica Section B: Structural Science
Volume	60
Issue number	2
DOIs	https://doi.org/10.1107/S0108768104001843
Publication status	Published - Apr 2004
Externally published	Yes

ASJC Scopus Subject Areas

General Biochemistry,Genetics and Molecular Biology

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title = "Calcium-lead fluoro-vanadinite apatites. II. Equilibrium structures",

abstract = "The synthetic vanadinites (PbxCa10-x)(VO 4)6(F1-2yOy□y) 2, 0.57 < x < 9 and 0.10 < y < 0.47, adopt the P6 3/m apatite structure with 9.7835 (3) ≤ a ≤ 10.0531 (1) {\AA} and 7.0318 (2) ≤ c ≤ 7.3033 (1) {\AA}. The calcium endmember is monoclinic, space group P21lm, with a = 9.7370 (3), b = 9.7358 (4), c = 7.00572 (9) {\AA}, y= 120.002 (5)°. For mixed metal compounds (x ≠ 0) the partitioning of calcium and lead over the AI(4f) and A II(6h) positions is nonstoichiometric, with lead preferentially favouring the larger AII site at a partitioning coefficient k Pb(AI/AII) ≃ 0.33 for all x < 7. A miscibility gap exists for 2 < x < 3. Trends in crystallographic parameters can be correlated through consideration of the AIO 6 metaprism twist angle (φ) that can be used to derive ideal cell parameters from triangular anion networks.",

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AB - The synthetic vanadinites (PbxCa10-x)(VO 4)6(F1-2yOy□y) 2, 0.57 < x < 9 and 0.10 < y < 0.47, adopt the P6 3/m apatite structure with 9.7835 (3) ≤ a ≤ 10.0531 (1) Å and 7.0318 (2) ≤ c ≤ 7.3033 (1) Å. The calcium endmember is monoclinic, space group P21lm, with a = 9.7370 (3), b = 9.7358 (4), c = 7.00572 (9) Å, y= 120.002 (5)°. For mixed metal compounds (x ≠ 0) the partitioning of calcium and lead over the AI(4f) and A II(6h) positions is nonstoichiometric, with lead preferentially favouring the larger AII site at a partitioning coefficient k Pb(AI/AII) ≃ 0.33 for all x < 7. A miscibility gap exists for 2 < x < 3. Trends in crystallographic parameters can be correlated through consideration of the AIO 6 metaprism twist angle (φ) that can be used to derive ideal cell parameters from triangular anion networks.

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Calcium-lead fluoro-vanadinite apatites. II. Equilibrium structures

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