Determining the crystal structure of Sr_5(PO_4)_3Br, a new compound in the apatite series, by powder diffraction modeling

摘要

Pentastrontium bromidephsphate, Sr_5(PO_4)_3Br, was prepared by solid state reaction. The crystal structure of polycrystalline Sr_5(PO_4)_3Br was refined from X-ray powder diffraction data by the Rietveld method using the structure model of Sr_5(PO_4)_3Cl single crystals. Sr_5(PO_4)_3Br is. Isostructural with Sr_5(PO_4)_3Cl. The space group is P6_3/m. The cell parameters are a_0 =9.9641(1) A. c_0=7.2070(1) A, α=β=90°, γ=120°, z=2, d(calc)=4.27 g/cm~3, and d(expt)=4.10g/cm~3. Atomic parameters are given. Final values are Rp=10.9/100, Rwp=14.3 /100, and S=1.28. The figure of merit is F30=58 (0.013, 39).