CRYSTAL-STRUCTURE OF KCAF3 DETERMINED BY THE RIETVELD PROFILE METHOD

Using the Rietveld profile method, the atomic coordinates and anisotro pic temperature factors of KCaF3 were refined. At room temperature, KC aF3 crystallizes in monoclinic B2(1)/m symmetry, with the lattice para meters: a = 8.754(2) Angstrom, b = 8.765(4) Angstrom, c = 8.760(5) Ang strom, beta = 90.48(3)degrees, V = 672.1(3) Angstrom(3), Z = 8. The re finement procedure was stopped when R-B = 0.05 and the Durbin-Watson s tatistic factor = 0.85 had been reached. The structure determined is r elated to the tilting of CaF6 octahedra of the a(-)b(+)c(-) type, whic h are responsible for the monoclinic distortion in perovskite crystals . (C) 1997 International Centre for Diffraction Data.