Structure of α-NaCaAlF6 determined ab initio from conventional powder diffraction data

Article abstract of DOI:10.1016/S0992-4361(98)80007-6

α-NaCaAlF₆ is prepared by solid state reaction as poor quality crystals. The structure is determined ab initio from conventional X-ray powder data. The cell is monoclinic, space group P2₁/c, Z = 8, with a = 8.7423(3) A, b = 5.1927(2) A, c = 20.3514(9) A and β = 91.499(2)°. The final Rietveld refinement leads to R_P = 10.6% and R_B = 5.2%. The structure is built up from isolated AlF₆ octahedra, interconnected by CaF₇ polyhedra sandwiched between layers of NaF₈ and NaF₇ polyhedra extending in the be plane. Elsevier.