DETERMINATION OF SPACE GROUP AND STRUCTURE FOR SYNTHETIC SVABITE: Ca5(AsO4)3F. P. Goodman, A. Schwartzman, School of Physics, University of Melbourne, Parkville, Vic. Australia 3052, B.Rodier, F. Lincoln, Department of Chemistry, University of Western Australia, Nedlands, W.A. Australia 6009; T.J. White, Ian Wark Research Institute, University of South Australia, The Levels, S.A., Australia 5098.
Although the structure of fluoro-apatite was established some 50 years ago1, the chemical analogue with As replacing P has never been investigated structurally, due primarilly to the fact that in its native form it is associated with numerous cation impurities. In this paper we present evidence to show that the As substitution causes the space group to shift from P63/m to P6322, as a result of a shift of the heavier cation from special to general positions. The structural change has been investigated in the solid solutions Ca5(AsxP1-xO4)3F, and it appears that the change occurs for x > 0.5, although a complete phase diagram has yet to be described.
Investigative methods include CBED and Rietveld refinements of powder x-ray data.
1C.A.Beevers and D.B.McIntyre (1946) Mineralogical Mag. 27, 870.