Determining the crystal structure of <i>Sr</i> ₅ ( <i>PO</i> ₄ ) ₃ <i>Br</i> , a new compound in the apatite series, by powder diffraction modeling

Abstract

Pentastrontium bromidephosphate, Sr 5 ( PO 4 ) 3 Br , was prepared by solid state reaction. The crystal structure of polycrystalline Sr 5 ( PO 4 ) 3 Br was refined from X-ray powder diffraction data by the Rietveld method using the structure model of Sr 5 ( PO 4 ) 3 Cl single crystals. Sr 5 ( PO 4 ) 3 Br is isostructural with Sr 5 ( PO 4 ) 3 Cl . The space group is P 6 3 / m . The cell parameters are a 0 =9.9641(1) Å, c 0 =7.2070(1) Å, α=β=90°, γ=120°, Z =2, d ( calc )=4.27 g / cm 3 , and d ( expt )=4.10 g / cm 3 . Atomic parameters are given. Final values are Rp =10.9%, Rwp =14.3%, and S =1.28. The figure of merit is F 30=58 (0.013, 39).